Bribe consisting of cake and sugar essentially (4)
I believe the answer is:
bung
'bribe' is the definition.
(I've seen this before)
'cake and sugar essentially' is the wordplay.
'cake' becomes 'bun' (bun is a type of cake).
'and' is a charade indicator (letters next to each other).
'essentially' means to look at the middle letters.
The middle letter of 'sugar' is 'g'.
'bun'+'g'='BUNG'
'consisting of' acts as a link.
(Other definitions for bung that I've seen before include "Rubber stopper" , "Spigot or cork" , "Somehow stop" , "Stopper for closing hole in barrel" , "could be a corker" .)