Editor's "leave it in" (4)
I believe the answer is:
stet
'editor's leave it in' 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" , "leave things as they were" , "Eg, molar" , "Ignore crossing" , "Ignore instruction to change" .)