Note proprietor takes depressant (6)
I believe the answer is:
downer
'depressant' is the definition.
('downer' can be a synonym of 'depressant')
'note proprietor' is the wordplay.
'note' becomes 'd' (musical note).
'proprietor' becomes 'owner' ('owner' can be a synonym of 'proprietor').
'd'+'owner'='DOWNER'
'takes' is the link.
(Other definitions for downer that I've seen before include "A sad thing" , "Depressing experience" , "In slang, a depressant drug" , "Informally a depressant drug" , "Saddening experience" .)