2016 Olympics host, informally (3)
I believe the answer is:
rio
'2016 olympics host informally' 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 "Flying Down to -, Astaire, Rogers film" , "Manchester United player in South American city, in short?" , "- Ferdinand, footballer" , "Port, -- de Janeiro" , "place of carnival" .)