Teacher very important for dunce? (6)
I believe the answer is:
donkey
'dunce?' is the definition.
(thesaurus)
'teacher very important' is the wordplay.
'teacher' becomes 'don' (don is a kind of teacher**).
'very important' becomes 'key' (I've seen this before).
'don'+'key'='DONKEY'
'for' is the link.
(Other definitions for donkey that I've seen before include "Domesticated animal" , "- Jacket, - work" , "Foolish person; animal" , "Burro" , "Mary's transport" .)