Here are the possible solutions for every other letter in this puzzle's grid clue
Answer
Clue
Relevancy
vowel
Clue
Every other letter in this puzzle's grid(!)
What every other letter of every answer in this puzzle is
roundrobin
Clue
Tournament in which every contestant plays against every other
ess
Clue
Last letter in most plurals (but not in this puzzle's six longest answers, which are the only plurals in this grid)
Definition
the letter S, also ES
four
Clue
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)
