Caspian Sea feeder (4)
I believe the answer is:
ural
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">caspian sea feeder</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ural that I've seen before include "Mountain range in Russia" , "Russian river giving name to mountain range" , "Russian river flowing into the Caspian Sea" , "Russian river, rising in the mountains between Europe and Asia" , "River feeding Caspian Sea" .)