Carnival location (3)
I believe the answer is:
rio
'carnival location' is the definition.
(Rio de Janeiro is famous for its carnival)
This is all the clue.
(Other definitions for rio that I've seen before include "(Golfer) in the sand" , "A Mexican river - like Grande" , "Brazilian city and port" , "The ... Grande borders Texas and Mexico" , "- Ferdinand, footballer" .)