Regretted being audibly obnoxious (4)
I believe the answer is:
rued
'regretted' is the definition.
('rue' can be a synonym of 'regret')
'audibly obnoxious' is the wordplay.
'audibly' shows a homophone (sound like).
'obnoxious' becomes 'rude' (rude can mean obnoxious or unpleasant).
'rude' sounds like 'RUED'.
'being' is the link.
(Other definitions for rued that I've seen before include "was remorseful" , "'Regretted, repented (4)'" , "Bitterly regretted" , "Was contrite about" , "Was sorry" .)