Love apple (6)
I believe the answer is:
'love apple' is the definition.
(I know that love apple can be written as tomato)
This is all the clue.
(Other definitions for tomato that I've seen before include "It used to be call a love-apple" , "Part of a BLT sandwich" , "Salad plant" , "A motto turned out to be fruit/veg" , "A glossy red fruit eaten as a vegetable" .)