Joke grasped by May Queen? (7)
I believe the answer is:
majesty
'queen?' is the definition.
(a queen is addressed as Your Majesty)
'joke grasped by may' is the wordplay.
'joke' becomes 'jest' (synonyms).
'grasped by' indicates putting letters inside (I've seen this in other clues).
'jest' placed inside 'may' is 'MAJESTY'.
(Other definitions for majesty that I've seen before include "Royal state" , "Regal dignity" , "title" , "Impressive beauty" , "Royal quality" .)