Spotted drugs of different colours (6)
I believe the answer is:
espied
'spotted' is the definition.
('espy' can be a synonym of 'spot')
'drugs of different colours' is the wordplay.
'drugs' becomes 'es' (ecstasy tablets).
'of different colours' becomes 'pied' (pied can mean multicoloured - eg the Pied Piper).
'es'+'pied'='ESPIED'
(Other definitions for espied that I've seen before include "Saw (archaic)" , "Watched" , "Caught sight of (poetic)" , "observed in literature" , "Glimpsed" .)