Green’s Dictionary of Slang

1. to go shares with, to join, to be a partner with.

1864, 1867, 1870		Hotten Sl. Dict.
1865		Leaves from Diary of Celebrated Burglar 125/1: He said he would do his share towards getting it and would expect to ‘stand in’ if it [i.e. a robbery] ‘came off to rights’.
1879		‘Autobiog. of a Thief’ in Macmillan’s Mag. (London) XL 505: If I lend you them [i.e. housebreaking tools] I shall want to stand in (have a share).
1880		W. Hooe Sharping London 36: Stand in, to take part in.
1883		Nat. Police Gaz. (NY) 3 Nov. 6/2: ‘Say, if you touch him, young feller, I’ve got to stand in on the deal’.
1899		Ade Fables in Sl. (1902) 56: Clarence stood in with the Toughest Push in Town.
1904		Sydney Sportsman (Surry Hills, NSW) 2 Mar. 8/5: [He] insinuatingly made a demand to ‘stand in’ with the four winners. They declined to share ‘their hard earnings’ with an [...] outsider.
1905		Marvel III:55 10: Believing themselves to be ‘standing in’ – or, in other words, entitled to a share.
1910		Truth (Perth) 1 Oct. 4/7: When they talk about ‘the old / Pot-an’-pan,’ / You will tumble that they mean / The ‘old man,’ / Who’s perhaps a ‘bonser bloke,’ / Who can nimbly ‘prig a poke’ / Or ‘can stand in any joke’ / You may plan.
1910		Wodehouse Gentleman of Leisure Ch. xvii: ‘Do you make much at this sort of game?’ he asked. [...] ‘Pots,’ he said, with some enthusiasm. ‘Pots. I tell you, if you’ll stand in—’.
1949		Monteleone Criminal Sl. (rev. edn).

2. to have a friendly or profitable understanding with, to be in league with, to be on good terms with.

1882		Cooper Amer. Pol. 199: The former quickly allied themselves with the Democrats, and thus carried the State, though Grant’s administration ‘stood in’ with the Radicals [DA].
1887		Lantern (N.O.) 14 May 3: I stan’ in wid de roughs.
1903		A.H. Lewis Boss 144: Billy did try to stand in with this duck; an’ say! he turned sore in a second.
1911		G. Bronson-Howard Enemy to Society 38: They’d never harm a pal, not for a million bucks, and so it’s handy to stand in with ’em.
1923		J. Fishman Crucibles of Crime 206: They are sneaks [...] who endeavor to ‘stand in’ with their superiors by tattling about others.
1934		‘Maxwell Grant’ ‘Murder Marsh’ in Shadow Oct. 🌐 It ain’t a bad idea to stand in with the bulls. That’s the way I play it nowadays.
1953		T. Runyon In For Life 117: A convict who wanted to play with the Chiefs had to stand in with a stool-pigeon-loving yard captain.
1955		B. Schulberg On the Waterfront (1964) 87: I never stood in good enough with Johnny Friendly.