Annoying child making racket? That's about right (4)
I believe the answer is:
brat
'annoying child' is the definition.
(I've seen this before)
'racket? that's about right' is the wordplay.
'racket?' becomes 'bat' (bat is a kind of racket).
'that's about' is an insertion indicator.
'right' becomes 'r' (common abbreviation).
'bat' placed around 'r' is 'BRAT'.
'making' is the link.
(Other definitions for brat that I've seen before include "annoying young fellow" , "Little terror" , "child - that's a nuisance" , "Spoilt child" , "Ill-mannered child" .)