Disturbance curtailed in South American city (3)
I believe the answer is:
rio
'south american city' is the definition.
(I've seen this before)
'disturbance curtailed' is the wordplay.
'disturbance' becomes 'riot' (I've seen this before).
'curtailed' means to remove the last letter.
'riot' with its final letter taken off is 'RIO'.
'in' is the link.
(Other definitions for rio that I've seen before include "... Grande, ... de Janeiro" , "A Mexican river - like Grande" , "(Golfer) in the sand" , "Port, -- de Janeiro" , "old capital" .)