Better make a speech after running a mile (10)
I believe the answer is:
ameliorate
'better' is the definition.
('ameliorate' can be a synonym of 'better')
'make a speech after running a mile' is the wordplay.
'make a speech' becomes 'orate' (I've seen this before).
'after' says to put letters next to each other.
'running' indicates anagramming the letters.
'a'+'mile'='amile'
'amile' is an anagram of 'ameli'.
'orate' after 'ameli' is 'AMELIORATE'.
(Other definitions for ameliorate that I've seen before include "Become better" , "Make (something) better" , "seen to improve" , "Make (a bad thing) better" .)