Teacher has bit of a classic (11)
I believe the answer is:
masterpiece
'a classic' is the definition.
(thesaurus)
'teacher has bit' is the wordplay.
'teacher' becomes 'master' (I've seen this before).
'has' says to put letters next to each other.
'bit' becomes 'piece' (synonyms).
'master'+'piece'='MASTERPIECE'
'of' is the link.
(Other definitions for masterpiece that I've seen before include "tour de force" , "Work of outstanding artistry" , "Great work" , "Chef d'oeuvre" , "Outstanding item of workmanship" .)