Dry watercourse (4)
I believe the answer is:
wadi
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">dry watercourse</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for wadi that I've seen before include "Seasonally dry watercourse" , "dry course" , "Rocky watercourse in N Africa" , "Seasonal water channel" , "Valley usually dry" .)