Irritable fictional friend of Mole and Toad (5)

I believe the answer is:

ratty

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'irritable' is the definition.
(I've seen this before)

I don't understand the rest of the clue.

(Other definitions for ratty that I've seen before include "Irritable (informal)" , "Fictional mole's chum" , "Short-tempered" , "One messing about in a boat" , "Bad-tempered, irritable as a rodent" .)

I've seen this clue in The Globe and Mail.

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