Ambush teacher with award in the auditorium (8)
I believe the answer is:
surprise
'ambush' is the definition.
(thesaurus)
'teacher with award in the auditorium' is the wordplay.
'teacher with' becomes 'sur' (I can't explain this - if you can you should give a lot more credence to this answer).
'award' becomes 'prize' ('prize' can be a synonym of 'award').
'in the auditorium' shows a homophone (sound like) (ie as heard on a stage).
'prize' sounds like 'prise'.
'sur'+'prise'='SURPRISE'
(Other definitions for surprise that I've seen before include "Something unexpected" , "One of spelt out words" , "Astound" , "is not what's expected" , "Take unawares" .)