Commissioner from China, with NCO, visiting sultanate (9)
I believe the answer is:
ombudsman
'commissioner' is the definition.
(I've seen this before)
'china with nco visiting sultanate' is the wordplay.
'china' becomes 'bud' (china [plate] is Cockney rhyming slang for 'mate').
'with' is a charade indicator (letters next to each other).
'nco' becomes 'sm' (abbreviation for sergeant major, a type of NCO).
'visiting' is an insertion indicator.
'sultanate' becomes 'oman' (I've seen this before).
'bud'+'sm'='budsm'
'budsm' going inside 'oman' is 'OMBUDSMAN'.
'from' acts as a link.
(Other definitions for ombudsman that I've seen before include "Commisioner" , "one appointed to investigate complaints" , "Official pursuing complaints against government departments" , "Official investigator of complaints" , "Commissioner investigating complaints by the public" .)