Shrewder retaining ball, male player (9)
I believe the answer is:
'player' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'shrewder retaining ball male' is the wordplay.
'shrewder' becomes 'wiser' (I can't justify this - if you can you should believe this answer much more).
'retaining' indicates putting letters inside (inserted letters are held or retained).
'ball' becomes 'o' (O looks like a ball).
'male' becomes 'man' (man is a kind of male).
'wiser' going around 'oman' is 'WOMANISER'.
Can you help me to learn more?
(Other definitions for womaniser that I've seen before include "Lady-killer" , "Don Juan" , "Lothario" , "Man amorously pursuing females" , "A rake" .)