Hi kiki, is it an across or down clue as the 'over' could be vital to the parse.
I.E.
down could mean one word 'over' another word.
across would denote the letters are reversed (over) from right to left.
Mischief is often imp in crosswords but that doesn't seem to help.
The paper will give the answer on Monday but no explanation (unless there's been an error in the clue).