Reveal former beau, model (6)
I believe the answer is:
expose
'reveal' is the definition.
(I know that reveal can be written as expose)
'former beau model' is the wordplay.
'former beau' becomes 'ex' (beau can mean a boyfriend).
'model' becomes 'pose' (model can mean to pose).
'ex'+'pose'='EXPOSE'
(Other definitions for expose that I've seen before include "Lay bare" , "Reveal or unmask" , "brings out crime" , "Disclose" , "Make visible or apparent" .)