Anyone can write ClueDay clues. You submit one six-letter word and five clues for it, ordered hardest to easiest, and if it runs it is published under your name.
What makes a clue set work: the answer is a common word with no proper nouns, the five clues point at different senses or contexts rather than restating one, and the last clue is close to obvious so nobody who spent all five is left stranded. Accepted submissions are published as written rather than rewritten.