Fruit used to flavor gin (4)
I believe the answer is:
sloe
'fruit used to flavor gin' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sloe that I've seen before include "Black fruit" , "Fruit often used for gin" , "Sour blackthorn fruit" , "Fruit of the blackthorn does't sound fast" , "Fruit steeped in gin to make a liqueur" .)