Got together and enjoyed a single drug (9)
I believe the answer is:
methadone
'drug' is the definition.
(methadone is a kind of drug)
'got together and enjoyed a single' is the wordplay.
'got together' becomes 'met' ('meet' can be a synonym of 'get together').
'and' is a charade indicator (letters next to each other).
'enjoyed' becomes 'had' (I've seen this in other clues).
'a single' becomes 'one' ('one' can be a synonym of 'single').
'met'+'had'+'one'='METHADONE'
(Other definitions for methadone that I've seen before include "Drug used in treating heroin addiction" , "Narcotic analgesic drug" , "Synthetic drug taken to replace heroin" , "Synthetic analgesic" .)