Crosophile initially took (consumed) an ace drug (9)
I believe the answer is:
methadone
'drug' is the definition.
(methadone is a kind of drug)
'crosophile initially took consumed an ace' is the wordplay.
'crosophile' becomes 'me' (where the crossword setter is 'Crosophile').
'initially' indicates taking the first letters.
'consumed' becomes 'had' ('have' can be a synonym of 'consume').
'an ace' becomes 'one' (synonyms).
The initial letter of 'took' is 't'.
'me'+'t'+'had'+'one'='METHADONE'
(Other definitions for methadone that I've seen before include "Synthetic analgesic" , "Drug used in treating heroin addiction" , "Synthetic drug taken to replace heroin" , "Narcotic analgesic drug" .)