A child of four (10)

I believe the answer is:

quadruplet

'a child of four' is the definition.

'child of four' is the wordplay.
I cannot quite see how this works, but
'child' could be 'quad' (I have seen 'Child of four ' mean 'quad' so perhaps 'child' could also mean 'quad') and 'quad' is found in the answer.
This may be the basis of the clue (or it may be nonsense).

(Another definition for quadruplet that I've seen is " part of big delivery".)

I've seen this clue in The Globe and Mail and The Irish News.

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