"Shorn", with a hard "r". Some regional accents--New England, some places in the South--might drop the "r" but a generalized American accent would pronounce it quite clearly.

Also, mostly in America "Shaun" (usually "Sean" or "Shawn") has a pretty broad "a" sound that would sound less like "shorn" even with a dropped "r" ("sho'n"). With the drawls we have here it would almost be two syllables: "SHAW-wun".