Short public disturbance in S American port (3)
I believe the answer is:
rio
's american port' is the definition.
(I know that Rio is South American)
'short public disturbance' is the wordplay.
'short' means to remove the last letter.
'public disturbance' becomes 'riot' (I've seen this before).
'riot' with its last letter taken away is 'RIO'.
'in' acts as a link.
(Other definitions for rio that I've seen before include "(Golfer) in the sand" , "A Mexican river - like Grande" , "Flying Down to -, Astaire, Rogers film" , "old capital" , "The ... Grande borders Texas and Mexico" .)