Main character in audition? (3)
I believe the answer is:
sea
'main' is the definition.
('sea' can be a synonym of 'main')
'character in audition?' is the wordplay.
'character' becomes 'see' (possible spelling of 'C' according to Chambers).
'in audition?' shows a homophone (sound like) (audition can mean hearing).
'see' is a homophone of 'SEA'.
(Other definitions for sea that I've seen before include "Part of ocean" , "Great expanse of water" , "Vast expanse" , "Expanse of salt water" , "Watery expanse" .)