яблоко раздора - (an) apple of discord / a bone of contention: “The ownership of the ancestral home has been a bone of contention between the two brothers for the last twenty ears.”
язык развязывается (развязался) - to have a tongue that runs away with one: “How your tongue ran away with you last night. You shouldn’t have told about your boss like that in front of so many people.”
яйца курицу не учат - don’t teach your grandmother to suck eggs
ярмарка тщеславия - vanity fair: reference to the world dominated by folly frivolity and show
ясно как Божий день - open as day: “Open as day, he made no secret of the fact that he was clone in the world.”