Lone royalist revolutionary (8)
I believe the answer is:
solitary
'lone' is the definition.
(I know that lone can be written as solitary)
'royalist revolutionary' is the wordplay.
'revolutionary' indicates an anagram.
'royalist' anagrammed gives 'SOLITARY'.
(Other definitions for solitary that I've seen before include "friendless" , "reclusive" , "Without company" , "On one's own" , "Isolated; hermit" .)