Ballerina's skirt (4)
I believe the answer is:
tutu
'ballerina's skirt' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tutu that I've seen before include "8 [BALLET] term" , "very short garment" , "In which dancer may appear" , "Ballerina's stiff skirt" , "South African archbishop, b. 1931" .)