Spice Girl greeting old king and wise man (8)
I believe the answer is:
melchior
'wise man' is the definition.
(one of the three wise men of the Nativity)
'spice girl greeting old king' is the wordplay.
'spice girl' becomes 'Mel C' (member of the Spice Girls).
'greeting' becomes 'hi' (hi is a kind of greeting).
'old' becomes 'o' (abbreviation).
'king' becomes 'R' (abbreviation for rex, king in Latin).
'melc'+'hi'+'o'+'r'='MELCHIOR'
'and' acts as a link.
(Other definitions for melchior that I've seen before include "magus" , "One of the three Magi" , "Foreign king" , "One of the Three Wise Men" .)