Try first-rate drug (5)
I believe the answer is:
crack
I believe this clue is a triple definition!
'try' is the first definition.
(I know that crack is a type of try)
'first-rate' is the second definition.
(I've seen this before)
'drug' is the third definition.
(crack is a kind of drug)
(Other definitions for crack that I've seen before include "Ace" , "Fracture" , "Thin fissure or slangy joke" , "attempt" , "Take severe measures - . . . . . down on" .)