Said in error, a lot (4)
I believe the answer is:
oral
'said' is the definition.
(I've seen this in other clues)
'in error a lot' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ORAL' can be found hidden inside 'error a lot'.
(Other definitions for oral that I've seen before include "See 18" , "Spoken exam" , "language exam" , "Spoken rather than written" , "Relating to the mouth - exam" .)