Green’s Dictionary of Slang

(US, also nutting time) the fundamental basics, usu. of a ruthless nature, ‘dirty work’.

1969		B. Jackson Thief’s Primer 133: Whenever you get down to the real nutcutting of it, you’re in bad trouble, you’d have to see if you can sell your car.
1987		T. Wolfe Bonfire of the Vanities 65: Forget it! It’s nut-cutting time.
2006		F.X. Toole Pound for Pound 120: Folks in these parts called it nut-cuttin time.