Work in toilet, topless, to get drug (8)
I believe the answer is:
atropine
'drug' is the definition.
(I've seen this before)
'work in toilet topless' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'in' indicates putting letters inside.
'toilet' becomes 'latrine' (latrine is a kind of toilet).
'topless' means to remove the first letter.
'latrine' with its first letter removed is 'atrine'.
'op' put within 'atrine' is 'ATROPINE'.
'to get' acts as a link.
(Other definitions for atropine that I've seen before include "Poisonous substance" , "Drug obtained from deadly nightshade" , "Poison found in deadly nightshade used as a drug" , "A pointer (anag) - belladonna" .)