Crossword puzzle clue "this puzzle has one"

Puzzle-within-a-puzzle puzzle

Mark that appears four times in this puzzle (hint: the baseball player who's the answer to this puzzle uses one, too)

Busy one that has made its mark in this puzzle's five longest answers

A crossword editor has to be very careful when changing one--unlike this puzzle's editor, who was careless four times herein

Each one in this puzzle has its year in parentheses

Word or phrase that has no repeated letters (every answer in this puzzle is an example of one)

This puzzle has one

This puzzle has one