Revolutionary gnome admired, not entirely an evil spirit (6)
I believe the answer is:
daemon
'an evil spirit' is the definition.
(daemon is a kind of evil spirit)
'revolutionary gnome admired not entirely' is the wordplay.
'revolutionary' says the letters should be written backwards.
'not entirely' indicates a hidden word.
'nomead' is hidden within 'gnome admired'.
'nomead' reversed gives 'DAEMON'.
(Other definitions for daemon that I've seen before include "guardian spirit" , "Evil spirit" , "Spirit in ancient Greek belief" .)