River feeding a larger one (9)
I believe the answer is:
tributary
'river feeding a larger one' is the definition.
(I've seen this before)
This is all the clue.
(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" .)