In theatre, hear selected play, in practice (8)
I believe the answer is:
rehearse
'practice' is the definition.
(I've seen this before)
'in theatre hear selected play' is the wordplay.
'in' indicates the answer is hidden within the clue.
'REHEARSE' can be found hidden inside 'theatre hear selected play'.
'in' acts as a link.
(Other definitions for rehearse that I've seen before include "prepare for performance" , "Practise (one's lines)" , "Practise before a public performance" , "Practise like actor" , "Cast practise for play" .)