A top teacher coming from Eton’s changed: "I’m English and progressive" (5,2,4,4)
I believe the answer is:
ahead of ones time
'progressive' is the definition.
(more progressive than typical for one's era)
'a top teacher coming from eton's changed i'm english' is the wordplay.
'top teacher' becomes 'head'.
'coming from' becomes 'of' (eg 'the food of France', food coming from France).
'changed' is an anagram indicator.
'english' becomes 'E' (abbreviation).
'etons' with letters rearranged gives 'onest'.
'a'+'head'+'of'+'onest'+'im'+'e'='AHEAD OF ONES TIME'
'and' is the link.
(Another definition for ahead of ones time that I've seen is " seen to be progressive".)