Strict, severe (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)
'severe' is the second definition.
(I know that severe can be written as stern)
(Other definitions for stern that I've seen before include "enforcing submission" , "Grimly serious; back" , "Where sailors may be" , "Back end of a ship" , "Strict, grimly serious" .)