Lugubrious (6)
I believe the answer is:
morose
'lugubrious' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for morose that I've seen before include "Lugubrious" , "in gloomy mood" , "Sullen and moody" , "Peevish and gloomy" , "Sullen and brooding" .)