Annulment referring to ring (6)
I believe the answer is:
repeal
'annulment' is the definition.
(I know that annulment can be written as repeal)
'referring to ring' is the wordplay.
'referring to' becomes 're' ('re' means regarding or about).
'ring' becomes 'peal' (pealing is a kind of ringing).
're'+'peal'='REPEAL'
(Other definitions for repeal that I've seen before include "'Annul, revoke (6)'" , "Annul an act of parliament" , "Abrogate" , "Annul a law" , "Rescind or withdraw a law" .)