Green’s Dictionary of Slang

a minor gangster, a small-time villain.

1935		Thieves Slang ms list from District Police Training Centre, Ryton-on-Dunsmore, Warwicks 11: Tear-away: A hooligan or thief who goes around blackmailing.
1938		F.D. Sharpe Sharpe of the Flying Squad 14: A type of crime which has almost died out now was carried out by thieves known as ‘Tearaways’ who used to hang about outside the theatres after the show and snatch costly brooches from women’s dress fronts.
1956		‘Raymond Thorp’ Viper 15: One or two I knew [...] as villains and tearaways who used the club for a contact place.
1957		P. Beveridge Inside the C.I.D. 71: These terros, or ‘tearaways’ as they styled themselves, began to give trouble in the clubs, demanding money and drinks and smashing furniture when they were refused.
1962		F. Norman Guntz 51: Another young geezer, who as it happened is a right tearaway.
1977		G.F. Newman Villain’s Tale 87: ‘Anyone in sight?’ ‘A couple of tearaways who might be worthwhile. I think it probably was a couple of kids,’ Brent informed the man.
1981		(con. c.1916) A. Harding in Samuel East End Und. 119: He was with some bloody tearaway.
1998		J. Hoskison Inside 161: Young tearaways get the impression that prison is a ‘breeze.’.
2000		J.J. Connolly Layer Cake 238: Mister Mortimer’s the large black fellow, bit of a tearaway.
2017		G. Gilmore Headland [ebook] ‘[W]hen I was your age I [...] was a right tearaway’.