Drug work — I scoffed (6)
I believe the answer is:
opiate
'drug' is the definition.
(opiate is a kind of drug)
'work i scoffed' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'scoffed' becomes 'ate' ('to scoff' is to eat).
'op'+'i'+'ate'='OPIATE'
(Other definitions for opiate that I've seen before include "A sleep-inducing drug (6)" , "Type of drug" , "Narcotic, such as morphine" , "Narcotic drug" , "Drug with an opium base" .)