Forbid an open arrangement with fruit (6)
I believe the answer is:
banana
'fruit' is the definition.
(type of fruit)
'forbid an open arrangement' is the wordplay.
'forbid' becomes 'ban' (banning is a kind of forbiding).
'open' says to take the initial letters (take the opening letter).
The first letter of 'arrangement' is 'a'.
'ban'+'an'+'a'='BANANA'
'with' is the link.
(Other definitions for banana that I've seen before include "Small politically unstable country dominated by foreign companies" , "Fruit grown in hands" , "Yellow-skinned fruit" , "Elongated edible fruit" , "Tropical yellow fruit" .)