Before Eve has a change of heart (3)
I believe the answer is:
ere
'before' is the definition.
(poetic term for 'before')
'eve has a change of heart' is the wordplay.
'eve has' becomes 'er' (I can't justify this - if you can you should believe this answer much more).
'a change' becomes 'leg' (leg is a kind of change).
'of heart' means to look at the middle letters (I've seen 'heart' mean this).
The centre of 'leg' is 'e'.
'er'+'e'='ERE'
Can you help me to learn more?
(Other definitions for ere that I've seen before include "Old word for before" , "Archaic word for before - a palindrome" , "Old prior" , "Before (in poetry)" , "Before (in time)" .)