Crossword puzzle clue "service turned down four times in this puzzle"

Service turned down four times in this puzzle

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

Number of times this puzzle's theme word appears diagonally in the grid (to complete the puzzle, shade those words plus the Down answers that begin where they meet)

It's turned down in turndown service

Collection consisting of four plates, four saucers, four bowls, etc.

Org. that has four teams with non-plural nicknames, which begin this puzzle's four longest answers

Cheerleader-turned-singer-turned-judge

Only tennis player who has won all four Grand Slam titles at least four times each