Comic revises gag to be belligerent (10)
I believe the answer is:
aggressive
'be belligerent' is the definition.
('aggressive' can be a synonym of 'belligerent')
'comic revises gag' is the wordplay.
'comic' is an anagram indicator.
'revises'+'gag'='revisesgag'
'revisesgag' anagrammed gives 'AGGRESSIVE'.
'to' acts as a link.
(Other definitions for aggressive that I've seen before include "Belligerent" , "Forceful" , "Combative - pushing" , "Showing anger" , "Rudely hostile" .)