Underskirt (9)
I believe the answer is:
petticoat
'underskirt' is the definition.
(I know that underskirt can be written as petticoat)
This is the entire clue.
(Other definitions for petticoat that I've seen before include "Slip" , "garment" , "London Lane" , "Woman's undergarment" , "Woman's underskirt" .)