Ratty manx weasel in Calais you encaged (9)

I believe the answer is:

verminous

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

I don't understand the rest of the clue.

(Other definitions for verminous that I've seen before include "Like fleapit" , "ratty" .)

I've seen this clue in the Sydney Morning Herald.

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