Crossword Genius

Premises of note? (4)

Ross

I believe the answer is:

flat

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This clue might be a double definition.

'premises' is the first definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.

'note?' is the second definition.
(thesaurus)

'of' is the link.

Can you help me to learn more?

(Other definitions for flat that I've seen before include "Level; pad" , "with no relief" , "Puncture" , "Pressing implement" , "character on the staff" .)

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