Here are the possible solutions for feature of this puzzle's three long down answers clue
Answer
Clue
Relevancy
eon
Clue
Long long long long long long long time
Definition
a long period of time, also AEON
stick
Clue
Feature of this puzzle's three long Down answers
wordsquare
Clue
Classic letter puzzle -- or, when parsed differently, a hint to three Down answers in this puzzle
tmi
Clue
Brief version of this puzzle's title hidden in eight long puzzle answers
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)
Definition
the cardinal number next above three
allfalldown
Clue
End of a nursery rhyme, or the fate of this puzzle's other three long answers
btw
Clue
Incidentally, in texting ... and a hint to three long puzzle answers
ins
Clue
What this puzzle's long answers each have three of
