A bit quiet in the auditorium (5)
I believe the answer is:
piece
'a bit' is the definition.
(a bit is a small piece)
'quiet in the auditorium' is the wordplay.
'quiet' becomes 'peace' (I've seen this before).
'in the auditorium' indicates a 'sounds like' (homophone) clue (ie as heard on a stage).
'peace' sounds like 'PIECE'.
(Other definitions for piece that I've seen before include "Musical composition" , "Component; portion" , "E.g. bishop" , "Morsel" , "one of eight once ready for the Spanish?" .)