More gloomy (6)
'more gloomy' is the definition.
('dark' can be similar in meaning to 'gloomy')
This is the entire clue.
(Other definitions for darker that I've seen before include "More gloomy" , "Less illuminated" , "More deficient in light" , "Dimmer, murkier" .)
'more gloomy' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bluer that I've seen before include "more despondent" , "more depressed" , "Wastrel" , "getting more down" , "More racy" .)