Apartment still gloomy (4)
I believe the answer is:
flat
I believe this is a triple definition!
'apartment' is the first definition.
(I know that apartment can be written as flat)
'still' is the second definition.
(thesaurus)
'gloomy' is the third definition.
(flat can mean gloomy or dull#)
(Other definitions for flat that I've seen before include "In music, below the correct pitch" , "not deep?" , "Digs perhaps" , "Absolutely" , "rooms exactly" .)