Is it possible to say you are "arranging a back-up", when for example you're afraid somebody is going to leave who always made your homework every sunday, and you are already trying to crimp someone else to do the job?
Well, if you are already preparing a replacement of something/someone, incase it/he wouldn't continue to do what it/he should do and currently is doing for you, can you call that activity "arranging a back-up"?
So is a conversation like this possible?
"Tom is planning to leave the country, so in a few months maybe you have to start doing your own homework!"
"Don't worry, I'm already arranging a back-up (=I'm already looking for another)."
I think that would be appropriate but I'm unsure what you mean by "made your homework" and "crimp someone else to do the job". Surely you don't mean that somebody else is doing your homework for you? Do you mean creating homework assignments?
"Arranging a back-up" could be that I work in a job where someone has to be there at all times. If I must leave for an appointment, I must "arrange for a back-up" person to replace me while I'm gone. So, if you're having someone else do something for you and you can't do it, then you would have to "arrange for a back-up" person to do it.