Leave the undergrowth, just cut it and let it lay. There may be something in it that is beneficial to your lone plant. Years ago we had to clear a bit of old cemetery that had all sorts of orchids growing, we moved the deep turfs to a similar site but the orchids disappeared. Even collecting the hay after the seed had set did not resulting orchids where it was spread. Where the lads had to keep a site tidy with cutting and strimming etc, the public used to rant and rave but the orchids always came back the following year. They are a mystery, but keep notes, you will be worth a fortune if you succeed where everybody else has failed.