Wisdom in place where everyone's over fifty? (8)

I believe the answer is:

sagacity

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'wisdom' is the definition.
(sagacity is a kind of wisdom)

I cannot understand how the remainder of the clue works.

(Other definitions for sagacity that I've seen before include "of judgments" , "Good judgement, wisdom or shrewdness" , "showing wisdom" , "good judgment?" , "It's a cagy kind of wisdom" .)

I've seen this clue in The Telegraph.

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