Badly behaved kid (4)
I believe the answer is:
brat
'badly behaved kid' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for brat that I've seen before include "A spoiled badly-behaved child" , "Irritating youngster" , "child - that's a nuisance" , "Spoilt child" , "Brash young type" .)