Cloaking is showing one page to the search engine and another page to the visitors. Since the visitor would see the same page if they entered in the same URL(
www.website.xxx/) directly, it's not cloaking.
But if someone clicks on a link for
www.website.xxx and you take the keyword from the referrer string and use that to show them search results, I think it is something between cloaking and not cloaking. Using something in the referrer to display content is not something I think I have heard of before, but is an interesting idea.
I would not think it was practical, since a page would get many different referrers. Still, if you look for "q=" for example, you could use this to show them what they were looking for on Google.
I think it's not a bad idea, but it's a matter of how many visitors are going to hit your site with that kind of referrer string that you can use?