The most common and most likely answer to this crossword clue is the 5 plus 3 letter word WATER RAT
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More clues leading to the result WATER RAT
- Raw treat prepared for amphibious rodent
- Pirate queen and artist captured by Scottish engineer
- Irrigate desert to find aquatic creature
- Treat raw waste that’s found in a river
- Scottish engineer admitting mistake with a boatman
- Pirate making endless mistakes, a rebel primarily
- Rodent in earth with Asian temple all around
- Pirate‘s charge for service reduced
Buddy explains!

The straight part
We know that "amphibious rodent" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case amphibious rodent = water rat.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.