Dirty work

[A] sort of little back kitchen, where dirty work, such as washing up dishes, might be done.

Source: wiktionary

"I am no telltale," said James scornfully. […] Jasper urged James to give information about Rodney, but he steadily refused. "I leave others to do such dirty work," he said.

Source: wiktionary

[M]any a business-man can say he doesn't do dirty work, because he has others do it for him.

Source: wiktionary

In a job like that you see the dirty work of Empire at close quarters. The wretched prisoners huddling in the stinking cages of the lock-ups, the grey, cowed faces of the long-term convicts, the scarred buttocks of the men who had been flogged with bamboos—all these oppressed me with an intolerable sense of guilt.

Source: wiktionary