Nude sort of mound (4)
I believe the answer is:
dune
'mound' is the definition.
(I have seen 'Mound of sand ' mean 'dune' so perhaps 'mound' could also mean 'dune')
'nude sort' is the wordplay.
'sort' is an anagram indicator.
'nude' with letters rearranged gives 'DUNE'.
'of' is the link.
(Other definitions for dune that I've seen before include "Mound of drifted sand" , "Coastal sand hill" , "Low hill of sand, called in a desert a barkhan" , "Ridge of wind-blown sand" , "Nude in the sand" .)