CHEAPSKATE

MAGNACARTADocument sealed at Runnymede in 1215 (5,5) THATDOESIT"Enough already!" METHUSELAHBiblical patriarch – bottle holding six litres of wine (10) MINDTHEGAPWarning on exiting tube train (4,3,3) STRIPPOKERCard game that's really taking off? MEMORYLANETake a nostalgic trip down this (6,4) CEREBRATEDThought before entering bet, card getting dealt (10) ZZBUALDRINAstronaut for whom a Pixar character is named ZZZZFUYWUYBear of children's rhyme SUPERWOMANShe flies American back every week to country (10) HIGHSTAKESWith a lot on the line, or a phonetic hint to 3-, 8-, 15-, and 23-Down BIGBROTHERUbiquitous leader is great alongside fellow union member (3,7) AUTHORSHIPWriting this, hour wasted filling a puzzle at the beginning (10) SOMEPEOPLE"Unbelievable!" ... or what 17-, 25-, 35- and 46-Across are made from, letter-wise?