Mysterious drug boy accepts drunk (8)
I believe the answer is:
esoteric
'mysterious' is the definition.
(I've seen this before)
'drug boy accepts drunk' is the wordplay.
'drug' becomes 'e' (e is another name for ecstasy).
'boy' becomes 'eric' (I've seen this before**).
'accepts' is an insertion indicator.
'drunk' becomes 'sot' ('sot' can be a synonym of 'drunk').
'e'+'eric'='eeric'
'eeric' going around 'sot' is 'ESOTERIC'.
(Other definitions for esoteric that I've seen before include "exclusive" , "Understood by only a few people" , "Arcane -- coteries (anag)" , "Secret; taught to few" , "Secret, private" .)