Comic's straight man (6)
I believe the answer is:
stooge
'comic's straight man' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for stooge that I've seen before include "Partner who is the butt of comedian's joke" , "Comedian's sidekick" , "Toes go wrong for the scapegoat" , "Comic's straight man" , "Yes-man" .)