Notes actress turning into a philosopher (9)
I believe the answer is:
descartes
'a philosopher' is the definition.
(I know that Descartes is a philosopher)
'notes actress turning' is the wordplay.
'notes' becomes 'de' (two musical notes).
'turning' indicates an anagram.
'actress' is an anagram of 'scartes'.
'de'+'scartes'='DESCARTES'
'into' acts as a link.
(Other definitions for descartes that I've seen before include "French mathematician and philosopher" , "One who thought" , "Cogito, ergo sum man" , "Rene --, philosopher" , "French philosopher, d. 1650" .)