Prosecutor up calling for confession (9)
I believe the answer is:
admission
'confession' is the definition.
(thesaurus)
'prosecutor up calling' is the wordplay.
'prosecutor' becomes 'da' (D.A. is an example).
'up' is a reversal indicator (in down clue: letters go upwards).
'calling' becomes 'mission' (I've seen this before).
'da' in reverse letter order is 'ad'.
'ad'+'mission'='ADMISSION'
'for' acts as a link.
(Other definitions for admission that I've seen before include "Acknowledgement < of entry" , "Entree" , "acceptance" , "for which one may be charged" , "Right to go in" .)