Whopper topper (5)
I believe the answer is:
onion
'whopper topper' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for onion that I've seen before include "Tear-jerking bulb" , "Cause of tears" , "Bulbous vegetable" , "Aromatic flavourful versatile vegetable" , "Pungent vegetable" .)