Pharmacist keeps note in box (7)
I believe the answer is:
chemist
'pharmacist' is the definition.
(synonyms)
'note in box' is the wordplay.
'note' becomes 'mi' (as in 'do re mi').
'in' is an insertion indicator.
'box' becomes 'chest' (chest is a kind of box).
'mi' going within 'chest' is 'CHEMIST'.
'keeps' is the link.
(Other definitions for chemist that I've seen before include "Drug seller" , "Nobel, say" , "Shop for drugs" , "He dispenses prescriptions" , "Pharmacist, apothecary" .)