Clue: One of Macbeth's witches, initiator of toil or ditto of trouble, boiling? (4)
Answer: TROT
Explanation: Definition: One of Macbeth's witches
Anagram (just about) of T[oil] OR T[rouble]. TROT is an old word for "and old woman, a crone": it appears in *The Taming of the Shrew*: "Why give him gold enough and marry him to a puppet or an aglet-baby; or an old trot with ne'er a tooth in her head?"