Stiffened undergarment (6)
I believe the answer is:
corset
'stiffened undergarment' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for corset that I've seen before include "Stiffened undergarment" , "female garment!" , "Sector (anag)" , "Stiff supportive undergarment" , "Female undergarment" .)