Leontes, King of Sicily, is a principal character in this Shakespeare play (3,7,4)
I believe the answer is:
the winters tale
'play' is the definition.
(Shakespeare play)
'leontes king of sicily is a principal character in this shakespeare' is the wordplay.
I cannot quite understand how this works, but
'king' could be 'er' (abbreviation for Edward Rex, various English kings) and 'er' is found within the answer.
'a' is present in the answer.
'character' could be 'he' (he is a kind of character) and 'he' is present in the answer.
'in' is within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for the winters tale that I've seen before include "The Bard's work" , "entertainment" , "Play" .)