Old Greek king perhaps banking on one retiring (6)
I believe the answer is:
minoan
'old greek' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'king perhaps banking on one retiring' is the wordplay.
'king perhaps' becomes 'man' (king is a kind of man).
'banking' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'retiring' shows that the letters should be reversed in order.
'on'+'i'='oni'
'oni' in reverse letter order is 'ino'.
'man' enclosing 'ino' is 'MINOAN'.
Can you help me to learn more?
(Other definitions for minoan that I've seen before include "Bronze Age civilisation" , "Great civilization of ancient Crete." , "Someone in Bronze Age Crete" , "Ancient culture of island at 4 Down" , "Prehistoric Cretan" .)