The Clear Cards are new cards that started to appear after the Sakura Cards had turned blank and clear. It was revealed, in Chapter 23, that new cards were created by Sakura herself without realizing it, due to the growth of her magical powers.
Unlike the either the Clow Cards or Sakura Cards, they do not begin with "The" before the name of the card.
As the name states, the cards have a clear background on both sides, but display different images on the front and back. They have a frame with with a moon on the left and the sun on the right, with a seven pointed star with smaller five pointed stars on each tip, at the top and a magic circle at the back.