Stern, or unpleasant (4)
I believe the answer is:
grim
This clue is a double definition.
'stern' is the first definition.
(I know that stern can be written as grim)
'unpleasant' is the second definition.
(similar in meaning)
(Other definitions for grim that I've seen before include "Dour, forbidding" , "Ghastly" , "Dour and severe" , "Harshly ironic" , "Frightful" .)