S American river (6)
(Other definitions for rio that I've seen before include "A Mexican river, may be grande" , "Location of next Olympic Games, in short" , "place of carnival" , "Flying Down to -, Astaire, Rogers film" , "- Ferdinand, footballer" .)
(Other definitions for amazon that I've seen before include "Strong, well-built woman" , "Legendary woman warrior and river" , "S. America's longest river" , "banker" , "Strong woman - large river" .)