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