Possible Clues:

• Each of its interior angles measures 135°
• Regular form over swindle catching mark
• Shape of Athens' Tower of the Winds
• Old court in the past primarily noted for many-sided shape?
• A month back, new plane shape
• Figure of old Charlie — with label attached
• Month before an attempt to acquire new figure
• Another name for Westminster's Central Lobby
• Figure needs energy in broken-down Acton
• Circle somehow can't go into figure with straight sides