Nobleman appointed to receive King (4)
I believe the answer is:
duke
'nobleman' is the definition.
(duke is a kind of nobleman)
'appointed to receive king' is the wordplay.
'appointed' becomes 'due'.
'to receive' means one lot of letters goes inside another.
'king' becomes 'k' (abbreviation for king in chess).
'due' enclosing 'k' is 'DUKE'.
(Other definitions for duke that I've seen before include "Nobleman of the highest rank" , "High hereditary title in Britain" , "Highest ranked British peer" , "Highest hereditary title in Britain" , "noble" .)