Nude sort of hill (4)
I believe the answer is:
dune
'hill' is the definition.
(I know that dune is a type of hill)
'nude sort' is the wordplay.
'sort' indicates an anagram.
'nude' is an anagram of 'DUNE'.
'of' is the link.
(Other definitions for dune that I've seen before include "Low hill of sand, called in a desert a barkhan" , "Sandy hill" , "Nude in the sand" , "Ridge of wind-blown sand" , "Ridge of sand created by wind" .)