Germanic language enthusiast taking one teacher back (7)
I believe the answer is:
frisian
'germanic language' is the definition.
(Frisian is an example)
'enthusiast taking one teacher back' is the wordplay.
'enthusiast' becomes 'fan' (fan is a kind of enthusiast).
'taking' means one lot of letters goes inside another.
'one' becomes 'I' (Roman numeral).
'teacher' becomes 'sir' (way of addressing a male teacher).
'back' shows that the letters should be reversed in order.
'i'+'sir'='isir'
'isir' back-to-front is 'risi'.
'fan' enclosing 'risi' is 'FRISIAN'.
(Other definitions for frisian that I've seen before include "Lower breed" , "Relating to some Dutch islands" , "Dutchman" , "islander" .)