Lay out trendy underwear (6)
I believe the answer is:
invest
'lay out' is the definition.
(thesaurus)
'trendy underwear' is the wordplay.
'trendy' becomes 'in'.
'underwear' becomes 'vest'.
'in'+'vest'='INVEST'
(Other definitions for invest that I've seen before include "Contribute money in hope of a return" , "Formally place in office" , "Lay siege" , "Eg, buy stocks and shares" , "sink" .)