Drunkard carrying heroin and crack (4)
I believe the answer is:
shot
'crack' is the definition.
('shot' can be a synonym of 'crack')
'drunkard carrying heroin' is the wordplay.
'drunkard' becomes 'sot' ('sot' can be a synonym of 'drunkard').
'carrying' means one lot of letters goes inside another.
'heroin' becomes 'h' ('H' can be a synonym of 'heroin').
'sot' enclosing 'h' is 'SHOT'.
'and' acts as a link.
(Other definitions for shot that I've seen before include "Goal attempt" , "Photo; try" , "Zoomed" , "Charge" , "injured or killed?" .)