Allocate fool a gin cocktail (6)
I believe the answer is:
assign
'allocate' is the definition.
(I've seen this in another clue)
'fool a gin cocktail' is the wordplay.
'fool' becomes 'ass' (both can mean a stupid person).
'cocktail' indicates an anagram.
'gin' anagrammed gives 'ign'.
'ass'+'ign'='ASSIGN'
(Other definitions for assign that I've seen before include "Allot, allocate" , "Allot, fix, appoint" , "Transfer (legal rights)" , "Appoint or ascribe." , "Determine" .)