Testy – Wind in the Willows character (5)
I believe the answer is:
ratty
I believe this clue is a double definition.
'testy' is the first definition.
(thesaurus)
'wind in the willows character' is the second definition.
(I've seen this before)
(Other definitions for ratty that I've seen before include "In a bad temper" , "infestation of vermin" , "Bad-tempered, irritable as a rodent" , "his friend being a dangerous driver" , "Mole's friend (The Wind in the Willows)" .)