Reveal a former attitude (6)
I believe the answer is:
expose
'reveal' is the definition.
(I know that reveal can be written as expose)
'a former attitude' is the wordplay.
'a former' becomes 'ex' (prefix meaning former or onetime).
'attitude' becomes 'pose' (attitude can mean a pose or stance).
'ex'+'pose'='EXPOSE'
(Other definitions for expose that I've seen before include "Lay bare" , "Lay out to view" , "Reveal, uncover" , "Uncover or unmask" , "Bring to light" .)