The antonyms for the phrase "low down and dirty" could be any combination of words that imply the opposite meaning. Some possibilities might include "honest and upright," "clean and respectable," "upstanding and virtuous," or "noble and honorable." These phrases would convey a sense of morality, ethics, and dignity, which stands in stark contrast to the derogatory and negative connotations of "low down and dirty." Other antonyms might include words like "high-minded," "altruistic," or "generous," which would suggest a level of benevolence and kindness that is the polar opposite of sneaky, underhanded behavior. Ultimately, the choice of antonyms will depend on the context and the specific shade of meaning that the writer wants to convey.