Underwear item and shirt for a child (4)
I believe the answer is:
brat
'for a child' is the definition.
(brat is a kind of child)
'underwear item and shirt' is the wordplay.
'underwear item' becomes 'bra' (I've seen this before).
'and' is a charade indicator (letters next to each other).
'shirt' becomes 't' (as in a T-shirt).
'bra'+'t'='BRAT'
(Other definitions for brat that I've seen before include "Annoying child" , "Little terror" , "Unpleasant child" , "Urchin" , "child - that's a nuisance" .)