Bad-tempered friend of Mole's (5)

I believe the answer is:

ratty

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'bad-tempered' is the definition.
(I've seen this before)

I can't explain the rest of the clue.

(Other definitions for ratty that I've seen before include "infestation of vermin" , "Fictional mole's chum" , "Irritable (colloq.)" , "Mole's friend (The Wind in the Willows)" , "with hump?" .)

I've seen this clue in The Mirror.

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