Crossword puzzle clue "kind of order or a hint to this puzzle's unusual construction"

Kind of order ... or a hint to this puzzle's unusual construction

Enola Gay, e.g. (and a hint to this puzzle's unusual feature)

Construction staples ... or a hint to this puzzle's theme

Hint (and a hint to this puzzle's theme)

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

Puzzle invented by Lewis Carroll (and a hint to this puzzle's theme)

Classic letter puzzle -- or, when parsed differently, a hint to three Down answers in this puzzle

Kind of club that's a hint to this puzzle's theme