There are no real ways of clearing the console properly, at least for standard C++. If you want to do it 'properly', you'll need to either use the native API for your operating system or a curses-like library.
Preferably neither, and you got it wrong anyway (you forgot it takes a string literal). There are many reasons why system is bad - really the only thing it should be used for are throw-away little scripts you are writing, though C++ isn't the optimal language for that kind of thing.