I've gone through a few of these boots myself. Not sure if they sometimes rub on something? I would check to make sure that the far end of the boot is still wrapped around the big opening on your steering rack and properly fastened and the small end is properly fastened on the tie rod. Make sure both boots aren't ripped.
This boot might be a bit of a red herring for the noise you are hearing though... The clunking could possibly be a CV joint. That often presents as a clunk while turning.
It wouldn't hurt to check your power steering fluid level too, since it's easy to do. In this case, I dont think fluid level is the issue though. I'm leaning towards CV joint.
You can find universal replacement steering boots on Amazon, and if yours are damaged I would urge you to replace them before the steering rack is damaged. (Hopefully THAT isn't the issue)