Have you ever wondered what complete relief means? I was wondering when my ball was near the cart path on #18. The lie wasn't great, and the cart path was definitely interfering with my stance, but the further right I went, the more a tree was going to be an issue.
So it means what it sounds like it means. If I'm taking relief from the cart path, my nearest point of relief has to be at least far enough to no longer be standing on the cart path. But then you get a club length from your nearest point of complete relief, so you can probably find a good spot.
I was able to get a stance on grass, and still not have the tree be too much in my way.