Fjord relative (3)
I believe the answer is:
ria
'fjord relative' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ria that I've seen before include "inlet between hills" , "Little girl" , "Drowned river valley now an inlet of the sea" , "Coastline feature, a drowned valley" , "Submerged valley" .)