Drunkards vandalised poster (6)
I believe the answer is:
topers
'drunkards' is the definition.
(toper can mean a drunken person)
'vandalised poster' is the wordplay.
'vandalised' indicates anagramming the letters.
'poster' is an anagram of 'TOPERS'.
(Other definitions for topers that I've seen before include "We regularly knock it back" , "Habitual imbibers" , "Heavy drinkers" .)