Fight dishonest sailor in South American port (4,6)
I believe the answer is:
fray bentos
'south american port' is the definition.
(port in Uruguay)
'fight dishonest sailor' is the wordplay.
'fight' becomes 'fray' (fray is a kind of fight).
'dishonest' becomes 'bent' (bent can mean corrupt).
'sailor' becomes 'os' (ordinary seaman).
'fray'+'bent'+'os'='FRAY BENTOS'
'in' is the link.
(Other definitions for fray bentos that I've seen before include "South American port" , "Uruguayan port city, once known for exporting corned beef -- by seafront (anag)" .)