Sec wine, dark (6)
I believe the answer is:
morose
'dark' is the definition.
(I know that dark can be written as morose)
'sec wine' is the wordplay.
'sec' becomes 'mo' (both can mean a small amount of time).
'wine' becomes 'rose' (rose is a kind of wine).
'mo'+'rose'='MOROSE'
(Other definitions for morose that I've seen before include "in gloomy mood" , "grouchy" , "Sullen and ill-tempered" , "Miserable" , "Sad" .)