Some of them pushed the drug (4)
I believe the answer is:
hemp
'drug' is the definition.
(I've seen this before)
'some of them pushed the' is the wordplay.
'some of' indicates a hidden word.
'HEMP' is hidden in the letters of 'them pushed the'.
(Other definitions for hemp that I've seen before include "Narcotic drug" , "Cannabis sativa" , "Marijuana" , "Plant for rope or pot" , "tea" .)