They're back numbers, child (3)

I believe the answer is:

son

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'child' is the definition.
(male child)

I cannot understand how the remainder of the clue works.

(Other definitions for son that I've seen before include "Native" , "Male descendant" , "Young boy" , "The kind of child" , "Male offspring" .)

I've seen this clue in the Evening Standard.

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