Acknowledgement of daughter employed in a legation (9)
I believe the answer is:
admission
'acknowledgement' is the definition.
(admission is a kind of acknowledgement)
'daughter employed in a legation' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'employed in' indicates putting letters inside.
'legation' becomes 'mission' (legation can mean a diplomatic mission).
'a'+'mission'='amission'
'd' put within 'amission' is 'ADMISSION'.
'of' acts as a link.
(Other definitions for admission that I've seen before include "Statement acknowledging the truth of something" , "Entree" , "Acknowledge of the truth of something" , "Permission to enter" , "charge for entrance" .)