Green’s Dictionary of Slang

contract n.

1. a paid assignment, usu. to murder someone but also sometimes to get them into a less severe form of difficulty; thus put/take out a contract on v., to arrange to have someone killed; contract killer n., a killer for hire.

[UK]F.W. Carew Autobiog. of a Gipsey 434: There’s more ways o’ killin’ a pig than cuttin’ ’is throat, and when I takes a contrac’ in ’and, I likes ter work it out shipshape.
[US](con. 1920s) ‘Harry Grey’ Hoods (1953) 51: People came to us with what we called ‘contracts.’ [...] Contracts to murder their business partners, sweethearts, brothers, [etc.].
[US]G. Scott-Heron Vulture (1996) 95: If a man puts a contract on another man, he really signs one on the whole community.
[US]N. Heard House of Slammers 85: His contract on Junior Blake seemed to have garnered him even more adherents.
[Aus]G. Disher Paydirt [ebook] ‘There’s a fucking contract out on him’.
[Ire]J. O’Connor Salesman 327: Someone in the flats is after tellin’ her there’s a contract out on me.
[UK]N. ‘Razor’ Smith Raiders 183: The fruitcakes, desperos and knuckle-draggers will fall over each other [...] to take the contract.
[Aus]L. Redhead Thrill City [ebook] They reckon he was hit over some sort of drug money — there was a contract out on him.

2. (US police) any form of corrupt agreement involving regular payments, e.g. to politicians, lawyers, the police.

[US](con. 1900-29) L. Katcher Big Bankroll 302: There were always ‘contracts,’ that euphemism for ‘fix’ or ‘favor’ [...] A [politician’s] call to a judge to arrange for bail. A call to a lawyer, informing him of a client who needed his services.
[US]J. Mills Report to the Commissioner 170: [H]e made it sound like a contract, a politician’s kid or something like that.
E.F. Droge Patolman 53: For the most part [payoffs] centered around gamblers who paid quite regularly, but they also included tow truck operators on accident scenes, city marshals on evictions, and other various ‘contracts’ or ‘scores’.
[US](con. 1965) J. Lardner Crusader 63: The task of collecting the pad money was shared by the cops regularly assigned to the sector. [...] Boyd informed David that he would have to ‘honor all the contracts’ if he wanted a permanent seat.