A gloomy little room can be depressing (6)
I believe the answer is:
sadden
'be depressing' is the definition.
I can't judge whether this defines the answer.
'a gloomy little room' is the wordplay.
'a gloomy' becomes 'sad' (I've seen this before).
'little room' becomes 'den' (den is a kind of room. I am not sure about the 'little' bit.).
'sad'+'den'='SADDEN'
'can' acts as a link.
Can you help me to learn more?
(Other definitions for sadden that I've seen before include "Make dejected" , "Make melancholy and distressed" , "Dismay" , "Upset" , "get down" .)