Royal Duke losing double topping of cheese (10)
I believe the answer is:
gloucester
'cheese' is the definition.
(thesaurus)
'royal duke losing double topping of' is the wordplay.
I cannot really understand how this works, but
'royal' could be 'er' (abbreviation for Elizabeth Regina) and 'er' is present in the answer.
'of' could be 'o' and 'o' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for gloucester that I've seen before include "part of 1 25 [KING LEAR]" , "Character in King Lear" , "City on the Severn" .)