Pad at the back of a skirt in olden days (6)
I believe the answer is:
bustle
(Other definitions for bustle that I've seen before include "Busy oneself noisily about the former feature of women's dress" , "Excited activity - or padding at rear of old skirt" , "Hustle and fuss" , "Sublet (anag)" , "Attachment to a Victorian woman" .)