If you no longer wish to see Smart Matches™ for a tree that you are being matched with, go to Family Tree > Smart Matches™. Sort the matches ‘By family trees’ (this is the default setting). View the matches that you have with a specific site. Next to each person’s name, you will see the ‘Review match’ option, which will take you to the Smart Match™. Below the match is a link to the consensus page for all of the matches for that individual.
Above the list of all the matches is the option to ‘Ignore this tree’:
Clicking on it will bring up the following window.