For "clear" you need all the X11 Category packages. I had the same issue when I trashed them after XWin.exe kept running into errors, then about a week later I noticed it missing in the rxvt (that's a terminal emulator that, at least with Cygwin, can run with XWindows or without it) that I had kept after uninstalling the xorg-x11 stuff).
You can download them using the cygwin-setup.exe utility with which you installed the parts you have already. Or if it was a Net install, read up on how to add to your downloads by that method.
If you're undertaking to learn the command line, cygwin is, imo, a great place to start. If you're looking to use a Unix/Linux environment as an alternative OS to Windows, I don't recommend it. In the latter instance, if it's your machine and you don't mind setting aside 15 or 20 gigabytes of hard drive space, I strongly suggest something like
Wubi, which is a way to get a full graphical Linux, with updates and the latest utilities etc, on a Windows machine without having to erase and partition your boot drive between the two systems.
Just a suggestion.
BZT