I don’t know what graft is but read what they wrote in the article.
Illicit profit by corrupt means. In the case of cops, collecting regular payments from business establishments for looking the other way.
Used in a sentence: Michael Armstrong, who was counsel to the Knapp Commission and went on to become chairman of the city's Commission to Combat Police Corruption, observed in 2012 "The attitude throughout the department seems fundamentally hostile to the kind of systematized
graft that had been a way of life almost 40 years ago."
