Underwear, extremely daring (7)
I believe the answer is:
bravery
'daring' is the definition.
(I've seen this before)
'underwear extremely' is the wordplay.
'underwear' becomes 'bra' (I've seen this before).
'extremely' becomes 'very' (I've seen this before).
'bra'+'very'='BRAVERY'
(Other definitions for bravery that I've seen before include "heroic behaviour" , "daring" , "Courage" , "Courageous quality" , "Valour" .)