One has to be ready for such nimbleness (7)

I believe the answer is:

agility

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'nimbleness' is the definition.
(synonyms)

I cannot understand how the remainder of the clue works.

(Other definitions for agility that I've seen before include "Spryness" , "The ability to move quickly and easily" , "dexterity" , "Physical ability to move nimbly and quickly" , "Physical nimbleness, easy movement" .)

I've seen this clue in The Irish News.

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