They're back numbers, child (3)

I believe the answer is:

son

I'm a little stuck... Click here to teach me more about this clue!

'child' is the definition.
(son is a kind of child)

I don't understand the remainder of the clue.

(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.

Want a hint initially instead of a full solution? Install my app