Republican deserting miserable creature? (5)

I believe the answer is:

moose

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

(Other definitions for moose that I've seen before include "US deer with enormous antlers" , "North American elk" , "Animal" , "North American deer" , "Large N American deer like European elk" .)

I've seen this clue in The Guardian.

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