Feel bitter or indignant about (6)
I believe the answer is:
resent
'feel bitter or indignant about' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for resent that I've seen before include "Feel affronted by" , "Don't like" , "Be offended by" , "Feel bitter or envious" , "Feel displeased or indignant about" .)