Why do I have to pretend that I want a career with a certain department store?

I'm applying for a Christmas job with them, and the job application form says "What do you want to achieve in your career with us?" In actual fact, I want a teaching istant job but most of those don't start until January. So working in the department store would only be in the interim, and with all due respect, it isn't the place where I want to climb the career ladder. What exactly should I put down as my answer?