Vicious drugs parties? (5)
I believe the answer is:
sides
'parties?' is the definition.
(eg the two parties in an argument)
'vicious drugs' is the wordplay.
'vicious' becomes 'sid' (Sid Vicious).
'drugs' becomes 'es' (ecstasy tablets).
'sid'+'es'='SIDES'
(Other definitions for sides that I've seen before include "Outer edges, left and right" , "Angles" , "Sports teams" , "More than one team" , "opponents?" .)