Ideally the answer to this should come from the employer: They should have plans and expectations for you.

But if you're asked, use this general framework:

You'll work hard to determine how your job creates value -- you won't just stay busy, you'll stay busy doing the right things.

You'll learn how to serve all your constituents -- your boss, your employees, your peers, your customers, and your suppliers and vendors.

You'll focus on doing what you do best -- you'll be hired because you bring certain skills, and you'll apply those skills to make things happen.

You'll make a difference -- with customers, with other employees, to bring enthusiasm and focus and a sense of commitment and teamwork.

Then just layer in specifics that are applicable to you and the job.