Antagonise wayward sergeant (8)
I believe the answer is:
estrange
'antagonise' is the definition.
(I've seen this before)
'wayward sergeant' is the wordplay.
'wayward' indicates anagramming the letters.
'sergeant' with letters rearranged gives 'ESTRANGE'.
(Other definitions for estrange that I've seen before include "Alienate -- sergeant (anag)" , "Make enemy of sergeant" , "Cause to be alienated" , "split up?" , "Drive away" .)