Suspect nut assembled in auditorium (7,7)
I believe the answer is:
colonel mustard
'suspect' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'nut assembled in auditorium' is the wordplay.
'nut' becomes 'colonel' (I can't justify this - if you can you should believe this answer much more).
'assembled' becomes 'mustered' (muster means to gather).
'in auditorium' indicates a 'sounds like' (homophone) clue (as the word might sound to an audience).
'mustered' sounds like 'mustard'.
'colonel'+'mustard'='COLONEL MUSTARD'
Can you help me to learn more?
(Another definition for colonel mustard that I've seen is " Murder suspect".)