Choose to applaud at first before interrupting stage work (8)
I believe the answer is:
operetta
'stage work' is the definition.
(I've seen this before)
'choose to applaud at first before interrupting' is the wordplay.
'choose' becomes 'opt' (I've seen this before).
'at first' indicates taking the first letters.
'before' becomes 'ere' (usually literary**).
'interrupting' indicates putting letters inside.
The first letters of 'to applaud' is 'ta'.
'opt'+'ta'='optta'
'optta' placed around 'ere' is 'OPERETTA'.
(Other definitions for operetta that I've seen before include "G&S production, perhaps" , "The Mikado or Pirates of Penzance, say" , "Light opera" , "G&S work, perhaps" , "Short musical drama" .)