Person behind the movement of drugs (6)
I believe the answer is:
pusher
'person' is the definition.
(pusher is a kind of person)
'behind the movement of drugs' is the wordplay.
I cannot really understand how this works, but
'movement' could be 'push' (push is a kind of movement) and 'push' is found in the answer.
'drugs' could be 'e' (somebody 'on E' could also be 'on drugs') and 'e' is present in the answer.
A single letter 'r' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for pusher that I've seen before include "A seller of drugs on the streets" , "See 20" , "Criminal who sells illegal drugs" , "Street seller of illegal drugs" .)