The most common and most likely answer to this crossword clue is the 4 letter word PUDU
P
U
D
U
More clues leading to the result PUDU
Buddy explains!

The straight part
We know that "S American native" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case s american native = pudu.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.
What does PUDU mean?
PUDU noun- A very small South American deer of the genus Pudu, native to the Andes.