Staff regret taking drug money (7)
I believe the answer is:
retinue
'staff' is the definition.
(I've seen this before)
'regret taking drug money' is the wordplay.
'regret' becomes 'rue' (to rue something is to regret it).
'taking' means one lot of letters goes inside another.
'drug' becomes 'e' (E is another name for ecstasy).
'money' becomes 'tin' (old-fashioned slang term for money).
'e'+'tin'='etin'
'rue' going around 'etin' is 'RETINUE'.
(Other definitions for retinue that I've seen before include "Group of followers" , "Train; attendants" , "Body of attendants" , "Body of retainers" , "Entourage, followers" .)