10ac - Coin that was rectangular? Normal shape for coin! (5); 11 ac - Summer featured days on the turn, shorter (5); 17ac - Game had by for example snowboarders (3-2-3-6), and 20d - Flamboyant if unattractive topless hosts it's understood (6). I think the answers are Obang, Adder, Pig-in-the-middle and Glitzy, but can someone help with parsing, Please?