Most daring underwear for both sexes (7)
I believe the answer is:
bravest
'most daring' is the definition.
(I've seen this before)
'underwear for both sexes' is the wordplay.
'underwear' becomes 'bra' (bra is a type of undergarment).
'for both sexes' becomes 'vest' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'bra'+'vest'='BRAVEST'
Can you help me to learn more?
(Other definitions for bravest that I've seen before include "Most courageous" , "Most valiant" , "Most daring" , "Most handsome" , "Most heroic" .)