It took me forever to find it, too. But the item that looks like a broken mirror is it.
There is no cheat in any mission in any 39 clues game!
mission 7 39 clues answer for here lies b. fore e . fines
arctic
yep
On a bookshelf at the top
there arent any
Boxes on Beechey Isle
Arctic is the code you have to type in.
Near the bookcase on the right.
good
456
first one is 567 i am working on the right one. but the left is 567