Green’s Dictionary of Slang

(orig. US Und.) to hire someone to kill or otherwise attack a specific individual.

1975		7 Mar. diary in I. Malloy Southie Won’t Go (1986) 84: A Boston policeman asked me later if I thought the incident had been ‘contracted,’ whether a boy had been paid to do it [i.e. push a plate of spaghetti in another student’s face].
1991		M.B. ‘Chopper’ Read Chopper From The Inside 32: Once he was contracted to do a hit on a major underworld figure.