Return tender love (4)
I believe the answer is:
eros
'love' is the definition.
(Greek god of love)
'return tender' is the wordplay.
'return' is a reversal indicator.
'tender' becomes 'sore' (synonyms).
'sore' backwards is 'EROS'.
(Other definitions for eros that I've seen before include "Greek name of Cupid" , "divinity" , "Group of instincts" , "very centre of London?" , "Sore about love god" .)