Nut, or the nuts, has more than one meaning in gambling, so context matters. At the poker table, the nuts is the best possible hand given the community cards. A royal flush is the ultimate nut hand, but on most boards it cannot be made. That means the nuts change as the flop, turn and river are dealt, and a player holding the nuts knows no other hand can beat theirs.
Away from the cards, the nut is the cost of running a casino, meaning the overheads it must cover before it makes a profit. That sense gives us the phrase cracking the nut. Players also use it for the amount they have decided to win in a day. If it is not clear which meaning someone has in mind, just ask. It saves a misunderstanding.