Strict, forbidding (5)
I believe the answer is:
stern
I believe this is a double definition.
'strict' is the first definition.
(I know that strict can be written as stern)
'forbidding' is the second definition.
(synonyms)
(Other definitions for stern that I've seen before include "Unpleasantly serious" , "Strict, austere" , "Severe; grimly serious" , "Stiff - back - not smiling" , "Demanding < back" .)