Lover boy angry after rejection (4)
I believe the answer is:
eros
'lover boy' is the definition.
(Greek love god)
'angry after rejection' is the wordplay.
'angry' becomes 'sore' (sore can mean angry or resentful).
'after rejection' is a reversal indicator.
'sore' reversed gives 'EROS'.
(Other definitions for eros that I've seen before include "Greek equivalent to Roman Cupid" , "London landmark" , "Greek god of sexual love, Cupid to the Romans" , "Arrow shooter" , "asteroid four hundred and thirty three" .)