The most common and most likely answer to this crossword clue is the 10 letter word VALPARAISO
I've seen this crossword clue in The Times
V
A
L
P
A
R
A
I
S
O
More clues leading to the result VALPARAISO
Buddy explains!

The straight part
We know that "S American city" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case s american city = valparaiso.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.