Disturb solitary supporter of the crown (8)
I believe the answer is:
royalist
'supporter of the crown' is the definition.
(a royalist supports the monarch)
'disturb solitary' is the wordplay.
'disturb' indicates an anagram (I've seen 'disturbed' mean this (the order of letters is disturbed)).
'solitary' is an anagram of 'ROYALIST'.
(Other definitions for royalist that I've seen before include "Advocate of the principles of monarchy" , "For queen" , "12 (anag)" , "one in civil war" , "Civil War participant" .)