Green’s Dictionary of Slang

clean adv.

1. honestly.

c.1495		Skelton Dyvers Balettys and Dyties Solacyous ii line 41: Play fayre-play, madame, and loke ye play clene, Or ells with gret shame your game wylbe sene.
1850		‘Ned Buntline’ G’hals of N.Y. 143: For my part, whenever I do a thing, I always like to do it clean!
1990		(con. early 1950s) J. Ellroy L.A. Confidential 25: You’ve probably got documentation worked around to let you off clean and crucify me.

2. (US) in profit.

1899–1900

C.L. Cullen Tales of the Ex-Tanks 21: How’d I make out? Oh, only about $50 to $100 a day, clean, that’s all.

SE in slang uses

In phrases

clean around the bend (adj.) [around the bend adj. + pun on advertising slogan for the lavatory cleaner Harpic]

utterly insane.

2001

M.A. Margetson ‘Computer Games’ [poem] 🌐 Some times they drive you crazy / Make your head feel hazy / Send you clean around the bend.

clean broke (adj.) (also clean busted) [broke adj.¹ ]

absolutely penniless.

1877		Era 18 Nov. 5/4: People told him that he would soon be ‘clean broke’.
1889		Dundee Courier 7 Jan. 3/5: A worthy widow [...] told me one of our bad years that ‘she would have been clean broke if it had not been for the strawberries.
1908		Derby Dly Teleg. 29 Sept. 2/8: Hill said he had been clean broke and willingly accepted £25 for his blood.
1910		J. London Burning Daylight Pt II Ch XIX 🌐 But suppose your prayer should be answered and I’d go clean broke and have to work for day’s wages?
1917		S. Lewis Job 246: ‘Well, little old trip [sic] made consid’able hole in my wad. I’m clean busted. Down to one hundred bucks in the bank.’.
1939		W. Winchell On Broadway 18 Feb. [synd. col.] There’s the lad who was clean broke recently, who didn’t have enough coin for a gallon of gas.
1947		Essex Newsman 12 Dec. 3/7: Most of us were clean broke and had no prospect even of gtting enough money to buy food.
1998		V. Lindsay ‘When Gassy Thompson Struck it Rich’ [poem] in Congo and Other Poems 🌐 The Swede had twenty cents, all right. / But Gassy Thompson was clean broke.

clean gone (adj.) [gone adj.¹ (1)]

utterly insane.

1887		W.T. Call Josh Hayseed in N.Y. 26: A clean-gone, love-struck gal.
1923		J. Manchon Le Slang.