Self-satisfied, giving sweets up (4)
I believe the answer is:
smug
'self-satisfied' is the definition.
(synonyms)
'sweets up' is the wordplay.
'sweets' becomes 'gums' (gum is a kind of sweet).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'gums' in reverse letter order is 'SMUG'.
'giving' is the link.
(Other definitions for smug that I've seen before include "Unctuous" , "Arrogantly complacent" , "Arrogantly self-satisfied" , "Prim" , "Showing excessive self-pride" .)