Part of play noticed in audience (5)
I believe the answer is:
scene
'part of play' is the definition.
('scene' is part of 'play')
'noticed in audience' is the wordplay.
'noticed' becomes 'seen' (I've seen this before).
'in audience' shows a homophone (sound like).
'seen' is a homophone of 'SCENE'.
(Other definitions for scene that I've seen before include "Excerpt from a play or film" , "Landscape; public display of anger" , "Picture" , "Section of a stage work" , "Landscape - tantrum" .)