Feel bitter about gift head disposed of (6)
I believe the answer is:
resent
'feel bitter' is the definition.
(I've seen this before)
'gift head disposed of' is the wordplay.
'gift' becomes 'present' (present is a kind of gift).
'head disposed of' means to remove the first letter.
'present' with its initial letter taken away is 'RESENT'.
'about' is the link.
(Other definitions for resent that I've seen before include "Feel or show annoyance" , "Find objectionable" , "Feel bad about" , "Consider (something) to be an affront" , "grudge" .)