Reverse 4wd, when wheel is turned, clucking sound
 

First time Jeep owner, traded in my 91 Full Size Bronco! :pirate:

Went into reverse and turned pretty hard (was still in 4wd), noticed a loud clunking (that horrible sound of metal, almost sounds like something will break!)

Sound was front passenger side.

I was also on a logging road that had stones as pavement, so the traction wasn't very good (slipping a little while backing up).

The wheel was turned pretty hard angle.

I did some research on this, and found it could be potentially a "Unit Bearing" or possibly the 4wd trying to disengage.

Any ideas what this could be for sure?

Welcome!

It's good the traction wasn't very good. Hard turning in 4WD on good surfaces can break things.

Check your front axle U-joint on that side. Look for play. Lots of Youtube videos on how to test it and change it. Anything by BleepinJeep is good. See also ChickBuilt and 1A Auto Parts for good Jeep vids.

If you are going in that far, take a good hard look at your ball joints and your hub (unit bearing) while you are at it.