Admirable woman last to go for drug (6)
I believe the answer is:
heroin
'for drug' is the definition.
(heroin is a kind of drug)
'admirable woman last to go' is the wordplay.
I cannot quite see how this works, but
'woman' could be 'her' (her refers to a woman) and 'her' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for heroin that I've seen before include "Highly addictive illegal drug" , "Class A drug" , "Narcotic powder derived from morphine" , "Highly addictive narcotic" , "Highly addictive morphine derivative" .)