Babysitter's handful (6)
(Other definitions for terror that I've seen before include "Alarm" , "Great fear" , "(What causes) panic" , "Fear - mischievous child" , "Young miscreant" .)
'babysitter's handful' 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 "child - that's a nuisance" , "Ill-behaved child" , "A spoiled, badly behaved child" , "Troublesome child" , "annoying young fellow" .)