Brazilian metropolis (3)
I believe the answer is:
rio
'brazilian metropolis' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rio that I've seen before include "The ... Grande borders Texas and Mexico" , "Location of next Olympic Games, in short" , "A Mexican river - like Grande" , "Flying Down to -, Astaire, Rogers film" , "(Golfer) in the sand" .)