Peel the source of this pus? (4,3)

I believe the answer is:

manx cat

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But I can't explain it at all! Could you help me understand?

(Other definitions for manx cat that I've seen before include "Feline without tail from neighbouring Isle" , "Tail-less feline from Isle of Man" , "Tailless animal" , "Tailless pet" , "Domestic feline lacking a tail (4, 3)" .)

I've seen this clue in The Times.

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