Unable to feel end of arm, roll over clutching it (4)

I believe the answer is:

numb

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'unable' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?

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

Can you help me to learn more?

(Other definitions for numb that I've seen before include "Lacking feeling" , "Anaesthetised, unfeeling" , "Deprived of feeling" , "Frozen" , "Without feelings" .)

I've seen this clue in The Times.

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