To greengrocer, say, Brazil's bananas (4)
I believe the answer is:
nuts
'bananas' is the definition.
(as in crazy)
I don't understand the rest of the clue.
(Other definitions for nuts that I've seen before include "out to lunch" , "Mast - mad" , "Barmy (colloq)" , "Fruit - bats" , "Crazy; food" .)