Drug injected in hand on joint (6)
I believe the answer is:
reefer
'joint' is the definition.
(informal term for a marijuana joint)
'drug injected in hand on' is the wordplay.
'drug' becomes 'e' (E is another name for ecstasy).
'injected in' indicates putting letters inside.
'hand on' becomes 'refer' (as in referring or handing something on to someone).
'e' going into 'refer' is 'REEFER'.
(Other definitions for reefer that I've seen before include "habit?" , "roll of hemp" , "A wool jacket; a spliff" , "drug-filled cigarette" , "Midshipman (sl.)" .)