Spy converted revolutionary spirit (6)
I believe the answer is:
psyche
'spirit' is the definition.
(I know that psyche is a type of spirit)
'spy converted revolutionary' is the wordplay.
'converted' indicates an anagram.
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'spy' with letters rearranged gives 'psy'.
'psy'+'che'='PSYCHE'
(Other definitions for psyche that I've seen before include "Immaterial part of a person" , "Sole and spirit" , "inner spirit" , "Human soul - Cupid's beloved" , "Eros's beloved" .)