Hi RapidFruity,
Welcome to the GLFW forums!
Using MinGW is somewhat complicated, so I would only recommend this to advanced developers over using the free Visual Studio Community compiler & IDE, or the cross platform Visual Studio Code C/C++.
Your error is due to not linking the GLFW library - see the GLFW documentation on building applications with MinGW. I don’t now how to add the a library to your configuration for CLion, but if you search I’m sure you can find the answer.
Alternatively you could try the GFLW CMake Starter, though I’ve not tried this with MinGW.
Cheers,
Doug.