Stopper; bribe (4)
I believe the answer is:
bung
I believe this clue is a double definition.
'stopper' is the first definition.
(I know that bung is a type of stopper)
'bribe' is the second definition.
(I've seen this before)
(Other definitions for bung that I've seen before include "sweetener" , "Bribe (slang)" , "Stopper for closing hole in barrel" , "could be a corker" , "Cask stopper" .)