If you refer to someone as a city slicker, you mean that they live and work in a city and are used to city life. the city slickers in the capital. A person with the sophisticated manner and dress traditionally associated by rural people with city dwellers. someone who lives and works in a city and has no experience of anything outside it - often used to show disapproval (slicker from slick (19-20 centuries), from SLICK)
{i} (Informal) person from a large city who is overly sophisticated, stylish and sophisticated city person, sophisticated city dweller