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Rhino, say, catches horny extremities in cramped movement (9)

Ross

I believe the answer is:

pachyderm

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'rhino' is the definition.
The answer and definition can be both animals as well as being singular nouns.
Perhaps you can see an association between them that I can't see?

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for pachyderm that I've seen before include "Insensitive sort" , "Large hoofed animal with a very thick skin" , "Thick-skinned mammal like elephant" , "Thick-skinned beast, such as a rhino" , "Elephant, hippo etc" .)

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