Comedian's act is run-of-the-mill (7)
I believe the answer is:
routine
I believe this clue is a double definition.
'comedian's act' is the first definition.
(I've seen this before)
'run-of-the-mill' is the second definition.
(thesaurus)
'is' is the link.
(Other definitions for routine that I've seen before include "Unvarying programme" , "boring" , "As a rule" , "Method" , "Normal course of action" .)