The most common and most likely answer to this crossword clue is the 5 letter word HUTIA
I've seen this crossword clue in The Guardian
H
U
T
I
A
Buddy explains!
The straight part
We know that "Rodent" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rodent = hutia.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 HUTIA mean?
HUTIA noun- Any of the medium-sized rodents of the family Capromyidae, which inhabit the Caribbean islands.