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 anagramming the letters.
'nude' with letters rearranged gives 'DUNE'.
'of' acts as a 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" .)