Pleased with oneself getting sweets back (4)
I believe the answer is:
smug
'pleased with oneself' is the definition.
(I've seen this before)
'sweets back' is the wordplay.
'sweets' becomes 'gums' (gum is a kind of sweet).
'back' says the letters should be written in reverse.
'gums' backwards is 'SMUG'.
'getting' is the link.
(Other definitions for smug that I've seen before include "Be envious of" , "Prim" , "Superior" , "Steal" , "Smirking" .)