Norwegian sea inlet (5)
I believe the answer is:
fiord
'norwegian sea inlet' is the definition.
'fiord' can be an answer for 'inlet' (fiord is a kind of inlet). I also know that both 'norwegian' and 'sea' relate to this answer.
This is the entire clue.
(Other definitions for fiord that I've seen before include "Long narrow sea inlet between high cliffs" , "Deep sea inlet as in Norway" , "Long, steep inlet from the sea" .)