Gin-flavoring fruit (4)
I believe the answer is:
'gin-flavoring fruit' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sloe that I've seen before include "Fruit steeped in gin to make a liqueur" , "Wild plum" , "Black fruit" , "Fruit of the blackthorn does't sound fast" , "Thorny bush with plum-like fruit" .)