Ridge directly obscures Norway (4)
I believe the answer is:
dune
'ridge' is the definition.
(I know that dune is a type of ridge)
'directly obscures norway' is the wordplay.
'directly' becomes 'due' (synonyms).
'obscures' is an insertion indicator (hides by surrounding with).
'norway' becomes 'n'.
'due' going around 'n' is 'DUNE'.
(Other definitions for dune that I've seen before include "Low hill of sand, called in a desert a barkhan" , "Seashore sand hill" , "Sandhill" , "Ridge of sand created by wind" , "Film" .)