If my page mentions a specific site and I want the top ad to link to that site without linking to it in the page copy can I do this?
If I understand correctly you want to set up a default ad that links to another site which is mentioned in your page copy. There shouldn't be a problem with that provided that the site doesn't violate the Adsense ToS.
But does it mean that it is ok to have a link from a competitor say BidV on the same page as Google Adsense? Would this be against Google TOS?
You can have a link to a competitor. You just can't have contextual ads, or ads that looks like Adsense ads, that appear on the same page as Adsense ads.