Crack cocaine handed down (5)
I believe the answer is:
cleft
'crack' is the definition.
(I know that crack can be written as cleft)
'cocaine handed down' is the wordplay.
'cocaine' becomes 'C' (drugs abbreviation).
'handed down' becomes 'left' (eg left in someone's will).
'c'+'left'='CLEFT'
(Other definitions for cleft that I've seen before include "Partially divided" , "Split (as a stick)" , "Split, divided" , "chasm" , "Split into two" .)