Lay out in underwear (6)
I believe the answer is:
invest
'lay out' is the definition.
(to lay out is to invest money)
'in underwear' is the wordplay.
'underwear' becomes 'vest'.
'in'+'vest'='INVEST'
(Other definitions for invest that I've seen before include "as Greeks did to Troy?" , "speculate?" , "Eg, buy stocks and shares" , "Contribute money in hope of a return" , "Lay out in expectation of profit" .)