Semi-aquatic rodent (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
coypu
(Other definitions for coypu that I've seen before include "South American rodent bred for its fur, nutria" , "Large South American aquatic rodent" , "Large semiaquatic rodent" , "aquatic mammal" , "Creature in fur coat" .)