More importantly, you should simply fix it. As either you have a canonical problem where Google is recognizing the same page as two separate pages because you don't provide a canonical page. Or you simply have the same Title and/or description on two separate pages. Either way they are easy fixes that Google WMT usually recognizes within a month of being fixed.
Thanks for the replies, The easiest way to fix the problem would be to simply remove my listing/link from the site that has it. right? How can I fix a canonical issue from my end If I cant get them to remove the link? Do I use this tag rel="canonical" on my index page?
Yes, that's a decent quick fix. Just use <link rel="canonical" href="http://www.example.com/"/>
More complex would be using a 301 redirect to remove the query strings. If you're not using any query strings, that's probably a better way to go. But if you are using some query strings, then it gets more complex - doable but complicated.
Actually, stripping all the query_strings is not that much more complex ... It can be done with a couple of lines in the .htaccess, and could easily be added to the canonicalization or other redirects ... ? at the end of the redirect strips it, so all that has to happen is a ? to be added to the current redirect locations and a condition added to the www non-www canonicalization that checks for a query string ... and it probably sounds more complicated to read about than it is.
You're right it is a bit more complicated, but not very much imo ... And, yes, the real 'complication' comes in if you need to remove 'most' but not the rest.