Critical figure to fifty per cent of Italians (5)

I believe the answer is:

vital

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'critical' is the definition.
(I know that critical can be written as vital)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for vital that I've seen before include "alive" , "Crucial" , "Necessary for life" , "Extremely important, essential to success" , "Critical, necessary" .)

I've seen this clue in the Evening Standard.

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