Conscious of a revolutionary green European (5)
I believe the answer is:
aware
'conscious of' is the definition.
(being conscious means being aware of something)
'a revolutionary green european' is the wordplay.
'revolutionary' shows that the letters should be reversed in order.
'green' becomes 'raw' (both can mean naive or inexperienced).
'european' becomes 'E' (abbreviation e.g. EU).
'raw' written backwards gives 'war'.
'a'+'war'+'e'='AWARE'
(Other definitions for aware that I've seen before include "Having knowledge (of fact)" , "Cognisant, mindful" , "well informed" , "Attentive" , "Conscious, sentient" .)