I am sorry to hear that your yucca is not doing too well.
It is hard to tell from your photo. Apart from needing to be repotted and given a good watering, it looks like it will be ok. Is this the stem that you are referring to?
Something else to consider is to give the roots a bit of a trim (remove the sections that appear to be circling around the pot) and then repot it and give it a good watering with a diluted fertiliser concentrate like seaweed emulsion. Please remember though that the pot should be well draining.
Good luck with this and I hope this helps.
Please ensure that you check back with any other questions or just to let us know how it is going :)