Philanderer, better advised around sultanate (9)
I believe the answer is:
womaniser
'philanderer' is the definition.
(I know this)
'better advised around sultanate' is the wordplay.
'better advised' becomes 'wiser' (wise can mean well-advised).
'around' indicates putting letters inside.
'sultanate' becomes 'oman' (I've seen this before).
'wiser' going around 'oman' is 'WOMANISER'.
(Other definitions for womaniser that I've seen before include "Man amorously pursuing females" , "Ladies' man" , "Playboy" , "Lothario" , "Wolf" .)