Email edited to make speech better (10)
I believe the answer is:
ameliorate
'better' is the definition.
(to ameliorate is to make better)
'email edited to make speech' is the wordplay.
'edited' indicates an anagram.
'to make speech' becomes 'orate' (oratory is public speaking).
'email' anagrammed gives 'ameli'.
'ameli'+'orate'='AMELIORATE'
(Other definitions for ameliorate that I've seen before include "Make (something) better" , "Make (a bad thing) better" , "Become better" , "seen to improve" .)