An area under prohibition for fruit (6)
I believe the answer is:
banana
'fruit' is the definition.
(banana is a kind of fruit)
'an area under prohibition' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'under' is a charade indicator (letters next to each other).
'prohibition' becomes 'ban' (ban is a kind of prohibition).
'an'+'a'='ana'
'ana' put after 'ban' is 'BANANA'.
'for' acts as a link.
(Other definitions for banana that I've seen before include "Fruity type" , "Tropical yellow fruit" , "Small politically unstable country dominated by foreign companies" , "Fruit that comes in a bunch" , "Curved yellow fruit" .)