King George holding on, no ruler (8)
I believe the answer is:
governor
'ruler' is the definition.
(thesaurus)
'king george holding on no' is the wordplay.
'king george' becomes 'gr' (Georgius Rex).
'holding' is an insertion indicator.
'on' becomes 'over' (I've seen this before**).
'over'+'no'='overno'
'gr' placed around 'overno' is 'GOVERNOR'.
(Other definitions for governor that I've seen before include "Ron, go rev up the state head" , "employer" , "Official in charge of town/region" , "Official appointed to rule" , "chief magistrate)" .)