EXCLUSIVE

A skin specialist who once got into an epic feud with Nicki Minaj is now in jail ... arrested for allegedly masterminding a MURDER FOR HIRE plot.

Dawn DaLuise owns her own salon -- Skin Refinery -- in West Hollywood. Another esthetician moved into the same building where DaLuise works and we're told she went ballistic at the threat of competition under her own roof.

Law enforcement sources tell TMZ ... DaLuise allegedly hired a hit man to kill her competitor. Sources tell us ... the would-be hit man is a VERY large, former Detroit Lions player.

We're told someone had loose lips and told an acquaintance about the murder-for-hire plot, and that person went to the L.A. County Sheriff's Dept. and blew the whistle.

DaLuise was arrested Wednesday for solicitation to commit murder and is currently being held on $1 million bail.

DaLuise has a huge celeb clientele, including Christian Slater, Sarah Michelle Gellar, Freddie Prinze Jr., Alicia Silverstone and Christina Ricci. She also claims Jennifer Aniston as a client.

Nicki Minaj was once a client, but that didn't go so well. DaLuise waxed Nicki's eyebrows, and Nicki went crazy, saying, "Look what you did to my damn face! You think this s*** is worth $170?!"