Picks up in the course of authentic practice session (9)
I believe the answer is:
rehearsal
'practice session' is the definition.
(rehearsal is a kind of practice session)
'picks up in the course of authentic' is the wordplay.
'picks up' becomes 'hears' (hearing is a kind of picking up).
'in the course of' is an insertion indicator.
'authentic' becomes 'real' (I've seen this before).
'hears' placed inside 'real' is 'REHEARSAL'.
(Other definitions for rehearsal that I've seen before include "Practice in theatre etc" , "preparation in house?" , "Practice session in preparation for public performance" , "Dummy run" , "Dramatic practice" .)