hard nut to crack

bone hard

As hard as a bone, rock hard.

bust a nut

To ejaculate.

cold hard cash

Money, regarded as an incentive that can override any doubts or ethical concerns.

crack a crust

To make a living.

crack a fat

To get an erection of the penis.

crack a smile

To smile, especially while attempting not to.

crack down

To take harsh action (against), as when enforcing a law more stringently than before.

crack of dawn

The first moment of daylight; the instant at which sunrise begins.