The King enters: "Let Handel composition be the last notes I'll hear" (5,5)
I believe the answer is:
death knell
'the last notes i'll hear' is the definition.
(a death knell signals a death)
'the king enters let handel composition' is the wordplay.
'the king' becomes 'k' (abbreviation for king in chess).
'enters' means one lot of letters goes inside another.
'composition' indicates anagramming the letters.
'let'+'handel'='lethandel'
'lethandel' anagrammed gives 'deathnell'.
'k' going within 'deathnell' is 'DEATH-KNELL'.
'be' is the link.
(Other definitions for death knell that I've seen before include "Parting note" , "Passing on ring" , "passing on rings" , "This will end all the hopes" , "Bell rung when someone's popped their clogs" .)