Andean stimulant (4)
I believe the answer is:
coca
'andean stimulant' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for coca that I've seen before include "Narcotic shrub" , "South American plant from which a narcotic drug is obtained" , "Drug-producing plant" , "Shrub whose leaves are chewed in the Andes as a stimulant" , "Source of drug" .)