Defy loud yob (5)
I believe the answer is:
flout
'defy' is the definition.
(thesaurus)
'loud yob' is the wordplay.
'loud' becomes 'f' (A musical term).
'yob' becomes 'lout' (I've seen this before).
'f'+'lout'='FLOUT'
(Other definitions for flout that I've seen before include "Mock" , "Ignore (rule)" , "Show blatant disregard for" , "Show contempt for (the law)" , "Disobey openly and scornfully" .)