Exaggerate concerning party (6)
I believe the answer is:
overdo
'exaggerate' is the definition.
(I know that exaggerate can be written as overdo)
'concerning party' is the wordplay.
'concerning' becomes 'over' (both can mean relating to).
'party' becomes 'do' (do can informally mean a party).
'over'+'do'='OVERDO'
(Other definitions for overdo that I've seen before include "Cook wrongly" , "Use to excess" , "Exhaust" , "Be excessive, say cook too long" , "Be excessive, perhaps cook too much" .)