Better people in education (5)
I believe the answer is:
Here is my best explanation:
'better' is the definition.
(emending is a kind of bettering)
'people in education' is the subsidiary indication.
'people' becomes 'men' (man is a kind of person).
'in' is an insertion indicator.
'education' becomes 'ed' (abbreviation - e.g. sex ed).
'men' placed within 'ed' is 'emend'.
(Other definitions for emend that I've seen before include "Make improvements or corrections", "Make changes to (a text)", "Remove errors", "Improve by editing", "Rectify", "Alter something written to correct errors", "Alter to improve (text)", "Make alterations", "Make correction in written material" and "Remove faults from".)