Mutilate badly in final (8)
I believe the answer is:
ultimate
'final' is the definition.
(similar in meaning)
'mutilate badly' is the wordplay.
'badly' indicates an anagram (letters in the wrong order).
'mutilate' anagrammed gives 'ULTIMATE'.
'in' acts as a link.
(Other definitions for ultimate that I've seen before include "The last element of a series" , "Mutilate in last possible way" , "Happening last" , "Last possible, final" , "Utmost; last" .)