Imprisoned scoundrel smuggling good drug (5)
I believe the answer is:
caged
'imprisoned' is the definition.
(I've seen this in another clue)
'scoundrel smuggling good drug' is the wordplay.
'scoundrel' becomes 'cad' (cad is a kind of scoundrel).
'smuggling' means one lot of letters goes inside another (some letters smuggled inside).
'good' becomes 'g' (abbreviation).
'drug' becomes 'e' (E is another name for ecstasy).
'g'+'e'='ge'
'cad' placed around 'ge' is 'CAGED'.
(Other definitions for caged that I've seen before include "Cooped up" , "Shut up" , "In a zoo?" , "in prison" , "Confined behind bars" .)