Disregard loud yobbo (5)
I believe the answer is:
flout
'disregard' is the definition.
(I know that flout is a more specific form of disregard)
'loud yobbo' is the wordplay.
'loud' becomes 'f' (short for forte - 'loud' in music).
'yobbo' becomes 'lout' (I've seen this in other clues).
'f'+'lout'='FLOUT'
(Other definitions for flout that I've seen before include "Ignore (rule)" , "Show contempt for (the law)" , "Disobey openly and scornfully" , "Treat with contempt" , "Show blatant disregard for" .)