The meta answer is PITY (Hint: Find a 4-letter noun.)
Four of the long Across answers end with syllables that sound like plurals of letters of the alphabet:
FLYINGTRA(PEZE) = Ps
JEOPARD(IZE) = Is
STRIP(TEASE) = Ts
TURNCLOCK(WISE) = Ys
This is where the puzzle's title, "Singular Kindness" comes into play. When you make those plural letter sounds "singular," you get P, I, T, and Y--which spells PITY, a 4-letter noun meaning "kindness" that satisfies the puzzle's hint.