A police department charges colonists getting drugs (8)
I believe the answer is:
'drugs' is the definition.
'a police department charges colonists' is the wordplay.
'police department' becomes 'cid' (I've seen this in other clues).
'charges' means one lot of letters goes inside another (charge can mean to charge into something).
'colonists' becomes 'ants' (ants live in colonies).
'acid' inserted inside 'ants' is 'ANTACIDS'.
'getting' acts as a link.
(Another definition for antacids that I've seen is "Medicines".)