Ill-behaved child (4)
I believe the answer is:
brat
'ill-behaved child' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for brat that I've seen before include "Spoilt child" , "Urchin" , "Bad child - pack member!" , "Unpleasant child" , "An obnoxious or spoiled child" .)