I wasn't sure either, so I just listed http://hubpages.com/@www on my application and it worked.
You can apply directly from the Hub Pages Affiliate Settings:
My account ---> Earnings --> Affiliate Settings: GoogleAdsense --> Set Up.
It will ask: "Do you already have a Google AdSense account?" If you answer, "no" it will bring up an application with some of information already filled in (ie. the URL for Hub Pages).
It might be easier to do it this way than through Google because I found the application process there glitchy. It kept telling me that someone already had an account with my email address - yes, ME! I have a Google account with other apps. and for some reason Google wouldn't let me use it for Adsense even though I was signed in when I started the application. Weird!
In Google help forums, I found that it was a HUGE problem with a lot of people and the viable solution offered by other users was to create a whole new Google account with a different email address solely for use with Adsense.
Sooooo, yeah. Try applying through Hub Pages first :-)