Drug dealer quietly meets doorkeeper (6)
I believe the answer is:
pusher
'drug dealer' is the definition.
(someone who sells or pushes drugs)
'quietly meets doorkeeper' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'meets' says to put letters next to each other.
'doorkeeper' becomes 'usher' (synonyms).
'p'+'usher'='PUSHER'
(Other definitions for pusher that I've seen before include "Street seller of illegal drugs" , "A seller of drugs on the streets" , "See 20" , "Criminal who sells illegal drugs" .)