Conduct from addict injecting heroin (5)
I believe the answer is:
usher
'conduct' is the definition.
(both can mean to lead or guide)
'addict injecting heroin' is the wordplay.
'addict' becomes 'user' (drug user).
'injecting' means one lot of letters goes inside another.
'heroin' becomes 'H' (synonyms).
'user' going around 'h' is 'USHER'.
'from' is the link.
(Other definitions for usher that I've seen before include "Doorkeeper in parliament or 29 down" , "Introduce" , "Minor court official" , "Theatre/cinema worker" , "Person showing one to a seat" .)