Don't strike! (4)
I believe the answer is:
stet
'don't strike' is the definition.
(printing term meaning leave alone or don't strike)
This is the entire clue.
(Other definitions for stet that I've seen before include "Instruction to cancel a deletion" , "Leave as is - don't amend" , "Instruction to keep" , "Printer's annotation - let it stand" , "(On proofs) instruction to cancel a correction" .)