Turn out to be in error about a point (4)
I believe the answer is:
oust
'turn out' is the definition.
(I've seen this in another clue)
'in error about a point' is the wordplay.
'in error' becomes 'out' (out can mean wrong or inaccurate).
'about' is an insertion indicator.
'a point' becomes 'S' (South).
'out' placed around 's' is 'OUST'.
'to be' is the link.
(Other definitions for oust that I've seen before include "Evict" , "Extract" , "Remove or reject from position" , "Drive out, expel" , "Expel from office or position" .)