Note penned by a politician said to be timeless (9)
I believe the answer is:
atemporal
'be timeless' is the definition.
'note penned by a politician said' is the wordplay.
'note' becomes 'te' (musical note).
'penned by' indicates putting letters inside (inserted letters are penned in).
'politician' becomes 'MP' (Member of Parliament).
'said' becomes 'oral' (both can mean spoken).
'a'+'mp'='amp'
'te' going within 'amp' is 'atemp'.
'atemp'+'oral'='ATEMPORAL'
'to' is the link.
(Another definition for atemporal that I've seen is " without considering the time?".)