Answer: houserule

AnswerCrossword Clue
HOUSERULELocal change in how a game is played
HOUSERULE"Dealer must draw to 16 or under," e.g.
HOUSERULEIt's not according to Hoyle
HOUSERULEGame twist
HOUSERULELocale-specific regulation
HOUSERULEGame changer?
HOUSERULEGame-changing invention?