Dark, gloomy (6)
I believe the answer is:
sombre
I believe this is a double definition.
'dark' is the first definition.
(I've seen this before)
'gloomy' is the second definition.
(I've seen this in other clues)
(Other definitions for sombre that I've seen before include "Dark, dull" , "Dull, gloomy" , "Gloomy and dismal" , "Joyless" , "Solemn and grave" .)