Ladies' man holding ancient city office (6)
I believe the answer is:
bureau
'office' is the definition.
(I know that office can be written as bureau)
'ladies' man holding ancient city' is the wordplay.
'ladies' man' becomes 'beau' (beau is a kind of man. I am not sure about the 'ladies'' bit.).
'holding' indicates putting letters inside.
'ancient city' becomes 'ur' (ancient Sumerian city state).
'beau' placed around 'ur' is 'BUREAU'.
Can you help me to learn more?
(Other definitions for bureau that I've seen before include "Wtiting desk" , "The B in the FBI" , "Piece of furniture with drawers" , "Foreign office" , "Item of furniture" .)