Some stage whispers (6)
I believe the answer is:
asides
'some stage whispers' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for asides that I've seen before include "Daises (anag.)" , "Remarks to an audience" , "not everyone hears them" , "Undertones on stage" , "Words spoken through side of mouth, not for all to hear" .)