Crossword Genius

River on the border between Spain and Portugal before flowing west to the Atlantic (5)

Ross

I believe the answer is:

douro

(Other definitions for douro that I've seen before include "European runner" , "Iberian river" , "Hollow bubbling sound" .)

I've seen this clue in The Mirror.
Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.