Green’s Dictionary of Slang

(orig. RAF) to run very fast; a euph. for go like hell under hell n.

1942		Hartlepool Mail 14 Aug. 2/3: The R.A.F. has developed a language all its own. [...] If a pilot is chased by the enemy he ‘goes like the clappers’.
1959		B. Naughton ‘Late Night on Watling Street’ in Late Night on Watling Street (1969) 8: You was goin’ like the clappers of hell.
1963		C. Wood ‘Spare’ in Cockade (1965) I i: Now remember – three bursts and up you go like the clappers.
1980		T. McClenaghan Submariners II ii: We’ve been going like the clappers.
1988		T. Jones Curse of the Vampire Socks 9: But they just went like the clappers.
1991		Reeves & Mortimer Vic Reeves Big Night Out n.p.: It went like the clappers!

a general intensive, extremely, a lot, very fast etc.

1948		Partridge Dict. Forces’ Sl. 42: Like the clappers (of hell), very fast. Mostly R.A.F.
1959		W. Hall Long and the Short and the Tall Act I: We’ll have to belt it like the clappers out of hell.
1965		G. Melly Owning Up (1974) 109: Her pitch was good and above all she could swing like the clappers.
1993		(con. 1945) S. McAughtry Touch and Go 114: You fancy me like the clappers.
1996		Penguin Bk of More Aus. Jokes 488: Flash Jack is off like the clappers – first gear, second gear.
1999		Indep. Rev. 13 July 11: Work like the clappers to achieve these aims.
2000		N. Griffiths Grits 449: I am a fuckin coward, ah yeh, av got no qualms abaht admittin that; first sign av lumba an am away like tha fucking clappers.
2001		M. Coles Bible in Cockney 83: Loads of people [...] who ran like the clappers.
2005		H. Mantel Beyond Black 164: She ran like the clappers out of hell, dropped dead two hours after.
2014		me-stepmums-too-fuckin-hot-mate at www.fakku.net 🌐 Soon’s the bell rings I’m off like the clappers.
2015		I. Welsh Decent Ride 72: Ma hert’s poundin away like the clappers.