Reads badly to vintage campaigner (8)
I believe the answer is:
crusader
'campaigner' is the definition.
(I've seen this before)
'reads badly to vintage' is the wordplay.
'badly' is an anagram indicator.
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'vintage' becomes 'cru' (e.g. grand cru).
'reads' anagrammed gives 'sader'.
'sader' put after 'cru' is 'CRUSADER'.
(Other definitions for crusader that I've seen before include "religious warrior" , "Champion" , "Campaigner -- rude scar (anag)" , "Vigorous campaigner" , "RA cursed (anag) - one fighting for a cause" .)