Woman in Athenaeum (3)
I believe the answer is:
ena
'woman' is the definition.
(feminine given name)
'in athenaeum' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ENA' is hidden in the letters of 'athenaeum'.
(Other definitions for ena that I've seen before include "- - Sharples (TV)" , "First name of Coronation Street's Widow Sharples, d. 1980" , "- - Sharples ('Coronation Street')" .)