Operatic prince to leave embraced by one king (4)
I believe the answer is:
igor
'operatic prince' is the definition.
(subject of Borodin opera)
'leave embraced by one king' is the wordplay.
'leave' becomes 'go'.
'embraced by' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'king' becomes 'r' (r is abbreviation for rex).
'i'+'r'='ir'
'go' going within 'ir' is 'IGOR'.
'to' is the link.
(Other definitions for igor that I've seen before include "Stravinsky's first name" , "Russian man" , "Prince of grand opera" , "Card game" , "-- Stravinsky, composer" .)