The most common and most likely answer to this crossword clue is the 4 letter word DEGU
D
E
G
U
Buddy explains!
The straight part
We know that "small Chilean rodent" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case small chilean rodent = degu.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 DEGU mean?
DEGU noun- Any species of the genus Octodon, especially Octodon degus, a small, caviomorph rodent native to Chile.