Hey Lycan,
Indirect lighting, as its name implies, illuminates areas that are not directly affected by lights. For instance, if you took a flashlight in a dark room and shown it at, lets say a desk, then the indirect light would still allow for you to see under that desk.
To disable the indirect lighting. Under the details panel of your light go to your Indirect Lighting Intensity and change that to 0.0. Then rebuild your lighting. This will disable the indirect lighting. It will just appear much less natural.
Here is a link to our documentation on lighting. I recommend going through it to tweak your lights to what you would like to see.
Thanks,