Dour (4)
I believe the answer is:
grim
'dour' is the definition.
(I know that dour can be written as grim)
This is the entire clue.
(Other definitions for grim that I've seen before include "Tight-lipped and foreboding" , "Severe; horrible" , "Frightful" , "Resolute" , "Dismal, dour" .)