Crossword Genius

Dull apartment (4)

Ross

I believe the answer is:

flat

I believe this clue is a double definition.

'dull' is the first definition.
(synonyms)

'apartment' is the second definition.
(I know that apartment can be written as flat)

(Other definitions for flat that I've seen before include "Not sloping; apartment" , "Lacking interest" , "Accommodation < still" , "like some races" , "razed to the ground, having had blow-out" .)

I've seen this clue in The Mirror and The Times.
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