Second wine is grim (6)
I believe the answer is:
morose
'is grim' is the definition.
(both can mean gloomy or sad)
'second wine' is the wordplay.
'second' becomes 'mo' (both are short periods of time).
'wine' becomes 'rose' (rose wine is a kind of wine).
'mo'+'rose'='MOROSE'
(Other definitions for morose that I've seen before include "dark" , "Sullen or glum." , "Rarely" , "Glum or sour-tempered" , "Silent, gloomy and ill-tempered" .)