Dour or stern (4)
I believe the answer is:
grim
This clue is a double definition.
'dour' is the first definition.
(I know that dour can be written as grim)
'stern' is the second definition.
(I know that stern can be written as grim)
(Other definitions for grim that I've seen before include "Very serious, gloomy" , "Very serious/gloomy" , "Frightful" , "Harsh and merciless" , "The - Reaper is death" .)