River feeding a larger one (9)
I believe the answer is:
tributary
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">river feeding a larger one</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tributary that I've seen before include "River that feeds a larger one" , "River flowing into another" , "River running into another" , "It helps create a larger flow" , "Stream flowing into a larger one" .)