Can I fix my auto white balance that's adjusting during my video clip using Premiere pro?

What grenadier is talking about is the HSL Secondaries tab of the Lumetri panel.

It's a two-part workflow in that tab.

The upper half is where you set a "key", the area that will be selected and affected by the controls down below in that tab. And the lower part are the controls to change the pixels selected by the key.

You can start a selection by eye-dropper which is a good way to start, and then improve the accuracy for your needs with the three sliders for Hue, Saturation, and Luma. But to see what your key is selecting, you need to set the mask ... I typically click it on, and set to color/gray. Then where my key is going to be selecting pixels to change, I will see the color. Everything else of the image is simply gray.

Now you can slide any of the key sliders sideways to change the center of the area chosen, modify the width of the three sliders to expand or shrink the area that slider chooses, and modify the feather, the width of the area that will be semi-selected.

Once you have the area selected you want to work on, you can use either a single color wheel/Luma slider control, or click on the three-wheel icon to get the full shadows/mids/highlights color wheel/luma controls available.

And below those are controls for saturation, contrast, sharpness ...

So you start a key, set the mask to check and modify the key, then uncheck the mask to see the change the controls below the key are modifying the image.

Neil