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

The straight part
We know that "Andean plateau" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case andean plateau = puna.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 PUNA mean?
PUNA noun- An alpine biological community in the central portion of the Andes in which short, coarse grass supports a Native American population.