Early historian, qualified teacher, English (4)
I believe the answer is:
bede
'early historian' is the definition.
(the Venerable Bede, 8th-century historian)
'qualified teacher english' is the wordplay.
'qualified teacher' becomes 'bed' (someone with a Bachelor of Education degree).
'english' becomes 'e' (abbreviation).
'bed'+'e'='BEDE'
(Other definitions for bede that I've seen before include "Historian saint; Eliot's Adam" , "Anglo-Saxon historian" , "Ancient English historian" , "Early English historian" , "Venerable author of The Ecclesiastical History of the English People, d. 735" .)