Feels bitter about gifts, but not at first (7)
I believe the answer is:
resents
'feels bitter' is the definition.
(to feel resentful is to feel bitter)
'gifts but not at first' is the wordplay.
'gifts' becomes 'presents' (present is a kind of gift).
'but not at first' means to remove the first letter.
'presents' with its initial letter taken away is 'RESENTS'.
'about' acts as a link.
(Other definitions for resents that I've seen before include "Begrudges" , "grudges" , "Takes offence" .)