That's a vendor-specific (and outdated) header file. It doesn't exist in modern standard C, nor does any modern C compiler (that I know of) support it.
In general, that's a platform-specific operation. There are some libraries (see CURSES) that are written for Windows and Linux that abstract terminal operations such as that. Even such a thing as "clearing the screen" is a complex operation that will require you to link to a 3rd party library that abstracts the complexity of that operation into a simple "clrscr" call.
Maybe you can simply remove the clrscr() call, and the include. There's really no reason for it in this simple program.