Are you sure you mean Cordyline and not Phormium? It's just that a Cordyline is unlikely to do this - it grows a thickish stem and the growth is usually at the top of the stem. Phormium, on the other hand, doesn't form a stem and the growth spreads sideways through the soil, with much longer leaves which will drape and cover other plants around. Assuming it is a Phormium, you can dig it up, split it and replant a section, which might help the surrounding plants, but in five years, the plants around will have also spread and thickened up, leaving less room for the Phormium anyway, so you might want to consider whether you take out some plants, or remove the Phormium altogether.

There are many dwarf phormiums which will probably suit the site better. Cutting the leaves not only looks very artificial, but they tend to turn brown at the cuts, making it look shopworn, as well as tortured.