1
general::
An unpleasant, distasteful, or thankless task or job. For example, Jane complained that she had to do all the dirty work while her colleagues took long vacations. [First half of 1900s]
American Heritage Idioms
2
general::
Phrase(s): dirty work
1. Fig. unpleasant or uninteresting work. • My boss does all the traveling. I get all the dirty work to do. • She’s tired of doing all the dirty work at the office. 2. Fig. dishonest or underhanded actions; treachery. • She knew there was some dirty work going on when she saw her opponents whispering together. • The company seems respectable enough, but there’s a lot of dirty work that goes on.
McGrawhill's American Idioms And Phrasal Verbs