Carp droppings picked up by SA rodent (5)

I believe the answer is:

coypu

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'rodent' is the definition.
(I know that coypu is a type of rodent)

I can't explain the rest of the clue.

(Other definitions for coypu that I've seen before include "Large South American aquatic rodent" , "aquatic mammal" , "rodents" , "South American rodent bred for its fur, nutria" , "Beaver lookalike" .)

I've seen this clue in The Independent.

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