diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 88a73df..2538224 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,6 +1,6 @@
 name: ci
 
-on: push
+on: pull_request
 
 jobs:
   build:
diff --git a/src/arctic3d/cli_resclust.py b/src/arctic3d/cli_resclust.py
old mode 100644
new mode 100755
index 7b70459..b242dcb
--- a/src/arctic3d/cli_resclust.py
+++ b/src/arctic3d/cli_resclust.py
@@ -23,6 +23,8 @@
     `linkage` : the linkage strategy.
 
     `criterion` : the criterion to extract the clusters.
+
+    `output` : the path where to output clusters data.
 """
 import argparse
 import sys
@@ -36,6 +38,7 @@
     get_clustering_dict,
 )
 from arctic3d.modules.input import Input
+from arctic3d.modules.output import create_output_folder
 
 
 argument_parser = argparse.ArgumentParser()
@@ -88,6 +91,13 @@
     "--chain", help="Segment ID to be considered", required=False
 )
 
+argument_parser.add_argument(
+    "--output",
+    help="Path to the generated output dictionary",
+    type=str,
+    required=False,
+)
+
 
 def load_args(arguments):
     """
@@ -128,7 +138,7 @@ def maincli():
     cli(argument_parser, main)
 
 
-def main(input_arg, residue_list, chain, threshold, linkage, criterion):
+def main(input_arg, residue_list, chain, threshold, linkage, criterion, output):
     """Main function."""
     log.setLevel("INFO")
 
@@ -192,14 +202,32 @@ def main(input_arg, residue_list, chain, threshold, linkage, criterion):
         )
 
         cl_dict = get_clustering_dict(clusters, unique_sorted_resids)
-        for el in cl_dict.keys():
-            log.info(
-                f"cluster {el}, residues"
-                f" {' '.join([str(res) for res in cl_dict[el]])}"
-            )
+
     else:
         log.info("Only one residue, no clustering performed.")
-        log.info(f"cluster 1, residues {unique_sorted_resids[0]}")
+        # fake cluster dict with only one entry
+        cl_dict = {1: unique_sorted_resids}
+    
+    # log data
+    for el in cl_dict.keys():
+        log.info(
+            f"cluster {el}, residues"
+            f" {' '.join([str(res) for res in cl_dict[el]])}"
+        )
+
+    # check if data must be flushed to output file
+    if output:
+        # initiate output directory
+        output_basepath = create_output_folder(output, uniprot_id='resclust')
+        # write txt file
+        log.info(f'writing clusters data in "{output_basepath}/Clusters.txt"')
+        with open(f'{output_basepath}/clustered_residues.out', 'w') as filout:
+            for el in cl_dict.keys():
+                filout.write(
+                    f"cluster {el} -> "
+                    f"{' '.join([str(res) for res in cl_dict[el]])}"
+                    "\n"
+                )
 
 
 if __name__ == "__main__":
diff --git a/src/arctic3d/modules/clustering.py b/src/arctic3d/modules/clustering.py
old mode 100644
new mode 100755
index 849c968..7686f8c
--- a/src/arctic3d/modules/clustering.py
+++ b/src/arctic3d/modules/clustering.py
@@ -127,10 +127,8 @@ def get_clustering_dict(clusters, ligands):
     cl_dict = {}
     # loop over clusters
     for cl in range(len(clusters)):
-        if clusters[cl] not in cl_dict.keys():
-            cl_dict[clusters[cl]] = [ligands[cl]]
-        else:
-            cl_dict[clusters[cl]].append(ligands[cl])
+        cluster_members = cl_dict.setdefault(cl, [])
+        cluster_members.append(ligands[cl])
     log.info(f"Cluster dictionary {cl_dict}")
     return cl_dict
 
diff --git a/tests/test_cli_resclust.py b/tests/test_cli_resclust.py
old mode 100644
new mode 100755
index 06f19d7..b1762a7
--- a/tests/test_cli_resclust.py
+++ b/tests/test_cli_resclust.py
@@ -2,6 +2,9 @@
 
 import pytest
 
+import os
+import shutil
+
 from arctic3d.cli_resclust import main
 
 from . import golden_data
@@ -22,6 +25,7 @@ def test_resclust_cli(example_pdbpath):
         7.0,
         "average",
         "distance",
+        None,
     )
 
 
@@ -35,6 +39,7 @@ def test_wrong_residue_list(example_pdbpath):
             9.0,
             "average",
             "distance",
+            None,
         )
     assert e.type == SystemExit
     assert e.value.code == 1
@@ -49,4 +54,21 @@ def test_resclust_maxclust(example_pdbpath):
         2,
         "average",
         "maxclust",
+        None,
     )
+
+
+def test_resclust_genoutput(example_pdbpath):
+    main(
+        example_pdbpath,
+        "100,101,102,133,134,135",
+        None,
+        2,
+        "average",
+        "maxclust",
+        "resclustout",
+    )
+    assert os.path.exists("resclustout") == True
+    assert os.path.exists("resclustout/clustered_residues.out") == True
+    shutil.rmtree("resclustout")
+