Approve turning up after drug treatment (5)
I believe the answer is:
enema
'treatment' is the definition.
(I know that enema is a treatment)
'approve turning up after drug' is the wordplay.
'approve' becomes 'amen' (I've seen this before).
'turning up' shows that the letters should be reversed in order.
'after' means one lot of letters go next to another.
'drug' becomes 'e' (E is another name for ecstasy).
'amen' backwards is 'nema'.
'nema' put after 'e' is 'ENEMA'.
(Other definitions for enema that I've seen before include "treatment by rear entrance" , "Bowel evacuator" , "In the end medical procedure" , "Procedure for vacating the bowels" , "process to ensure evacuation" .)