Refer to old nationalist revolutionary as intellectual (6)
I believe the answer is:
noetic
'intellectual' is the definition.
(I've seen this in another clue)
'refer to old nationalist revolutionary' is the wordplay.
'refer to' becomes 'cite' (synonyms).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'nationalist' becomes 'n' (abbreviation in politics).
'revolutionary' says the letters should be written in reverse (letters revolve around).
'cite'+'o'+'n'='citeon'
'citeon' reversed gives 'NOETIC'.
'as' acts as a link.
(Other definitions for noetic that I've seen before include "Relating to the intellect" , "Intellectual" , "Of a mind" .)