Comedian's bit (3)
I believe the answer is:
gag
'comedian's bit' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gag that I've seen before include "Humorous anecdote or remark" , "Stifle; joke" , "Kind of muzzle or informal joke" , "Choke; joke" , "Funny" .)