An economist generally doesn't work in business. An economist works for a university, a think-tank (like The Brookings Institution), or a government.
Someone who works in finance generally works in business, usually in banking, in the stock market (like at a brokerage firm), or for a corporation.
That said, economics does have some relevancy to finance, although not vice versa. You will not find a business degree, which includes finance degrees, offered anywhere that doesn't require a solid foundation in economics. My business degree required me to take three economics courses: micro economics, macro economics, and price-theory of economics. The purpose for that is to work in business, one must understand the environment, which economic systems are the environment in which businesses operate. Those economics courses, however, were not taught by the business college or the finance department but by the college of social sciences' economics department.