Worthy adversary's last on mail run after correction (8)
I believe the answer is:
luminary
'worthy' is the definition.
(I've seen this before)
'adversary's last on mail run after correction' is the wordplay.
'last' says to take the final letters.
'on' means one lot of letters go next to another.
'after' is a charade indicator (letters next to each other).
'correction' is an anagram indicator (I've seen this in other clues).
The last letter of 'adversary' is 'y'.
'mail'+'run'='mailrun'
'mailrun' anagrammed gives 'luminar'.
'y' after 'luminar' is 'LUMINARY'.
(Other definitions for luminary that I've seen before include "star" , "Eminent person or light-giving body" , "famous person" , "Leading light" , "Person of influence" .)