Express disapproval over usherette's top and skirt (4)
I believe the answer is:
tutu
'skirt' is the definition.
(tutu is a kind of skirt)
'express disapproval over usherette's top' is the wordplay.
'express disapproval over' becomes 'tut' (I've seen this in other clues).
'top' suggests taking the first letters.
The initial letter of 'usherette' is 'u'.
'tut'+'u'='TUTU'
'and' is the link.
(Other definitions for tutu that I've seen before include "The old primate" , "In which dancer may appear" , "Archbishop Desmond" , "Short dress" , "Ballet dancer's costume" .)