Revealed to be inaccurate (3)
I believe the answer is:
out
I believe this clue is a double definition.
'revealed' is the first definition.
(as in news which is out)
'inaccurate' is the second definition.
(eg a calculation might be 'out')
'to be' acts as a link.
(Other definitions for out that I've seen before include "what batsman doesn't want to be" , "Absent; away" , "Known" , "Escaped" , "Free" .)