Ridge of sand (4)
I believe the answer is:
dune
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ridge of sand</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for dune that I've seen before include "Sandhill" , "Film" , "Ridge of sand created by wind" , "Mound of drifted sand" , "Coastal sand hill" .)