If I understand your question correctly you're referring to the list of "Possible Matches" that comes up in the "Web Search" window after you click on a leaf.
There's no way I know to eliminate a match from this list without requerying (is that a word?) the matches by going back to the "People" window and clicking on the leaf again.
Each time you requery the matches anything you've already attached or ignored will be gone from the list.
Ignore everything above if you're initiating your search from the "Web Search" window.