Proof mark (4)
I believe the answer is:
stet
'proof mark' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for stet that I've seen before include "Printer's annotation - let it stand" , "Let it stand (L)" , "Direction in printing to cancel a correction or deletion" , "Notation meaning as is, thus" , "Restorative direction needed" .)