Greengrocer using apostrophes: 'Vegetable's and topping's for fruit' (5)
I believe the answer is:
guava
'fruit' is the definition.
(guava is a kind of fruit)
'greengrocer using apostrophes vegetable's and topping's' is the wordplay.
'topping's' says to take the initial letters (in a down clue, the letters at the top).
The first letters of 'greengrocer using apostrophes vegetables and' is 'GUAVA'.
'for' acts as a link.
(Other definitions for guava that I've seen before include "Pear-shaped tropical fruit" , "Tropical fruit with yellow skin and pink flesh" , "Tropical fruit with yellow skin and pink pulp" , "South American fruit" , "Tropical tree with yellow fruit" .)