The most common and most likely answer to this crossword clue is the 4 letter word PACA
P
A
C
A
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The straight part
We know that "Spotted rodent" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case spotted rodent = paca.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 PACA mean?
PACA noun- Any of the large rodents of the genus Cuniculus (but see also its synonyms), native to Central America and South America, which have dark brown or black fur, a white or yellowish underbelly and rows of white spots along the sides.