Vulgar undergarments extremely sexy (6)
I believe the answer is:
brassy
'vulgar' is the definition.
('brassy' can be a synonym of 'vulgar')
'undergarments extremely sexy' is the wordplay.
'undergarments' becomes 'bras' (bra is a kind of undergarment).
'extremely' says to hollow out the word (remove centre letters).
'sexy' with its middle removed is 'sy'.
'bras'+'sy'='BRASSY'
(Other definitions for brassy that I've seen before include "Tasteless and loud" , "Audacious" , "Showy - harsh" , "Tastelessly showy, loud" , "lacking taste" .)