Young Simpson nudging along a spoilt child (4)

I believe the answer is:

brat

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'spoilt child' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for brat that I've seen before include "Nasty little kid" , "Spoilt kid" , "Little terror" , "Marie ---, birth-control pioneer" , "Unpleasant youngster" .)

I've seen this clue in The Guardian.

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