Note seen in apartment (4)
I believe the answer is:
flat
I believe this clue is a double definition.
'note' is the first definition.
(thesaurus)
'apartment' is the second definition.
(I know that apartment can be written as flat)
'seen in' acts as a link.
(Other definitions for flat that I've seen before include "Featureless" , "Small residence - lacking sparkle" , "Unnatural - uninteresting - apartment" , "One at a meeting" , "Apartment - below the note" .)