Anger, possibly hate (4)
I believe the answer is:
heat
'anger' is the definition.
(I've seen this in another clue)
'possibly hate' is the wordplay.
'possibly' indicates an anagram.
'hate' anagrammed gives 'HEAT'.
(Other definitions for heat that I've seen before include "Preliminary round in a contest" , "Apply warmth" , "Get agitated" , "Toast" , "Raise temperature" .)