Was sorry to have sounded rude (4)
I believe the answer is:
rued
'was sorry' is the definition.
(I've seen this before)
'sounded rude' is the wordplay.
'sounded' indicates a 'sounds like' (homophone) clue.
'rude' sounds like 'RUED'.
'to have' is the link.
(Other definitions for rued that I've seen before include "Was contrite about" , "Bitterly regretted" , "'Regretted, repented (4)'" , "was remorseful" , "Was sorry" .)