Fruit; flop (5)
I believe the answer is:
lemon
This clue is a double definition.
'fruit' is the first definition.
(I know that lemon is a type of citrus fruit)
'flop' is the second definition.
(I've seen this in another clue)
(Other definitions for lemon that I've seen before include "Pulsate" , "Melon (anag)" , "fruit is on offer" , "Fruit-tree" , "Fruit (which is proverbially "the answer")" .)