Work helping to overcome drug use (9)
I believe the answer is:
operation
'use' is the definition.
(thesaurus)
'work helping to overcome drug' is the wordplay.
'work' becomes 'op' (common abbreviation for 'opus').
'helping' becomes 'ration' (a ration is a serving or helping).
'to overcome' indicates putting letters inside (some letters come over or go around others).
'drug' becomes 'e' (E is another name for ecstasy).
'op'+'ration'='opration'
'opration' placed around 'e' is 'OPERATION'.
(Other definitions for operation that I've seen before include "working" , "management" , "Manoeuvre - military action" , "Theatre procedure" , "performance" .)