Insult, loud, in a van (7)
I believe the answer is:
affront
'insult' is the definition.
(synonyms)
'loud in a van' is the wordplay.
'loud' becomes 'f' (short for forte - 'loud' in music).
'in' indicates putting letters inside.
'van' becomes 'front' (van can mean the front part of something).
'a'+'front'='afront'
'f' placed inside 'afront' is 'AFFRONT'.
(Other definitions for affront that I've seen before include "Snub" , "Cause of outrage or offence" , "provocation" , "not trivial offence" , "Action causing outrage or offence" .)