Not that which makes hits (4)
I believe the answer is:
this
'not that' is the definition.
(this one as opposed to that one)
'makes hits' is the wordplay.
'makes' is an anagram indicator.
'hits' with letters rearranged gives 'THIS'.
'which' acts as a link.
(Other definitions for this that I've seen before include "What's here" , "Hits (anag.)" , "The thing under discussion" , "near thing" , "Pronoun to point out nearby things" .)