Painful spot upset love god (4)
I believe the answer is:
eros
'love god' is the definition.
(Greek god of love)
'painful spot upset' is the wordplay.
'painful spot' becomes 'sore' (I've seen this in another clue).
'upset' is a reversal indicator.
'sore' back-to-front is 'EROS'.
(Other definitions for eros that I've seen before include "One worshipped" , "Famous statue in Piccadilly, London" , "divinity" , "Name given to statue" , "In Greek myth, the god of love" .)