Criminal attacked one left out (5)
I believe the answer is:
felon
'criminal' is the definition.
(I know that criminal can be written as felon)
'attacked one left out' is the wordplay.
'attacked' becomes 'f' (I can't explain this - if you can you should believe this answer much more).
'left' becomes 'l' (common abbreviation).
'out' is an anagram indicator (out can mean wrong or inaccurate).
'one'+'l'='onel'
'onel' with letters rearranged gives 'elon'.
'f'+'elon'='FELON'
(Other definitions for felon that I've seen before include "sore" , "Convicted criminal" , "convict" , "Person who has committed a serious crime" , "Mighty" .)