Pass over question one in no-good sullen seminar (10)

'no-good sullen seminar' is the definition.
'colloquium' can be an answer for 'seminar' (thesaurus). I'm not sure about the 'no-good sullen' bit.

'pass over question one in' is the wordplay.
'pass' becomes 'col' (col is a term for a mountain pass).
'over' becomes 'loum' (I can't justify this - if you can you should give a lot more credence to this answer).
'question' becomes 'qu' (abbreviation).
'one' becomes 'i' (Roman numeral).
'in' indicates putting letters inside.
'qu'+'i'='qui'
'loum' going around 'qui' is 'loquium'.
'col'+'loquium'='COLLOQUIUM'