The phrase "doest it" is a Middle English archaic form of the modern English phrase "does it." The word "do" is a common verb that expresses action or behavior in the present tense. Synonyms for this phrase could be "performs it," "executes it," "completes it," "accomplishes it," or "fulfills it." These synonyms convey the idea of carrying out a task or action. Additionally, other synonyms could include "handles it," "deals with it," or "addresses it," which suggest dealing with a problem or situation. Overall, there are many synonyms that could be used in place of "doest it," depending on the context of the sentence.