Reveal former stance (6)
I believe the answer is:
expose
'reveal' is the definition.
(exposing is a kind of revealing)
'former stance' is the wordplay.
'former' becomes 'ex'.
'stance' becomes 'pose'.
'ex'+'pose'='EXPOSE'
(Other definitions for expose that I've seen before include "article on scandal?" , "Revelation of something discreditable - remove cover" , "Bring to light" , "Uncover, expose to view" , "Lay bare" .)