Jamjar, at that height I'm going to assume you're actually talking about a Cordyline (google it to see) and not a Yucca. If you are, check the trunk for signs of rotting, oozing, and in particular orange gunk coming out. If the trunk is clear, wait - the plant may yet produce new growth up the stem, or from the base, or both, and you can then cut back to that, but you might have to wait till June for that to happen. If there is rotting present, keep an eye on it for now - it should be cut back past the rotted area, but that's best done in April if you want to try to give the plant a chance.