Badge: A lion rampant, holding a dagger in its paw.

Tartan: Since the clan MacDuff was not prominent in the later years of Scottish history, this tartan is similar to the royal Stewart without the white and yellow lines. There is a modern hunting tartan. 

Septs of the Clan: Duff, Fife, Fyfe, Spence, Spens, Wemyss.

The Scottish Tartan Society Lists several  different tartans for clan Mac Duff. The one in the left margin is listed as  "Clan MacDuff" and is tartan #1453. 

Tartan is Clan McDuff