Pitt the very much younger? (4)

I believe the answer is:

brad

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'pitt' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?

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

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(Other definitions for brad that I've seen before include "-- Pitt, US actor" , "Type of nail" , "Small tapered nail" , "One may secure" , "Small-headed nail" .)

I've seen this clue in the Evening Standard.

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