I think cash - It's a sort of box, and a cache is somewhere you can keep things safe.
I'm not 100% certain, but I prefer this to "case" - Casing a joint isn't really anything to do with safety, and a case isn't really abox, anywsay...
I also agree with case, as you do things just in case as a safety measure, and case is box. What do you get for 11 A, Attend, but worn out. ?E?T. Is it BEAT ?