Error makes it incorrect (7)
I believe the answer is:
mistake
'error' is the definition.
(I know that error can be written as mistake)
'makes it incorrect' is the wordplay.
'incorrect' is an anagram indicator.
'makes'+'it'='makesit'
'makesit' with letters rearranged gives 'MISTAKE'.
(Other definitions for mistake that I've seen before include "Error" , "Oversight" , "Fault" , "16 down" , "Wrong action or judgment" .)