Babysitter's bane (4)
I believe the answer is:
brat
'babysitter's bane' 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 "Irritating youngster" , "Unpleasant youngster" , "Spoilt child" , "A spoiled badly-behaved child" , "Mervyn -- (Titus Groan)" .)