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