Old king and Queen embodying superior majesty (8)
I believe the answer is:
grandeur
'majesty' is the definition.
(both can mean greatness or splendour)
'old king and queen embodying superior' is the wordplay.
'old king' becomes 'GR' (Georgius Rex, Latin for King George).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'embodying' is an insertion indicator (to embody can mean to contain or include).
'superior' becomes 'u' (I've seen this in other clues).
'er' going around 'u' is 'eur'.
'gr'+'and'+'eur'='GRANDEUR'
(Other definitions for grandeur that I've seen before include "Splendour; high rank" , "Loftiness" , "Majesty (God's, Hopkins)" , "Pomp" , "Nobility, dignity" .)