South American river port (3)
I believe the answer is:
rio
This clue might be a double definition.
'south american river' is the first definition.
'rio' can be an answer for 'river' ('river' in Spanish). I'm not sure about the 'south american' bit.
'port' is the second definition.
(Rio de Janeiro is a port)
Can you help me to learn more?
(Other definitions for rio that I've seen before include "Location of next Olympic Games, in short" , "Port, -- de Janeiro" , "... Grande, ... de Janeiro" , "Manchester United player in South American city, in short?" , "(Golfer) in the sand" .)