Wild plum (4)
I believe the answer is:
sloe
'wild plum' is the definition.
(sloe is a kind of wild plum)
This is all the clue.
(Other definitions for sloe that I've seen before include "Sour blue-black fruit" , "Fruit steeped in gin to make a liqueur" , "Fruit often used for gin" , "Musical study" , "Blackthorn, used in making a type of gin" .)