Absolved former politician to appear in film (6)
I believe the answer is:
exempt
'absolved' is the definition.
(I've seen this before)
'former politician to appear in film' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'politician' becomes 'MP' (Member of Parliament).
'to appear in' indicates putting letters inside.
'film' becomes 'ET' (E.T. the Extra-Terrestrial).
'mp' inserted inside 'et' is 'empt'.
'ex'+'empt'='EXEMPT'
(Other definitions for exempt that I've seen before include "Not liable to, immune" , "free from tax, say" , "Privileged" , "Absolved" , "Not liable to, excused" .)