Felt remorse (4)
I believe the answer is:
rued
'felt remorse' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rued that I've seen before include "was remorseful" , "Was contrite about" , "Was sorry" , "Bitterly regretted" , "'Regretted, repented (4)'" .)