Rear to be strict (5)
I believe the answer is:
stern
This clue is a double definition.
'rear' is the first definition.
(the stern is the rear of a boat)
'be strict' is the second definition.
(synonyms)
'to' is the link.
(Other definitions for stern that I've seen before include "Harsh at the back of the ship" , "having a forbidding appearance" , "Rents out at rear of boat" , "Hard - back" , "Rear of a vessel" .)