This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
宎 combines 宀 (roof) with 夭. The exact historical development is uncertain, and no widely accepted etymology is available for this rare character.
With no clear meaning, picture a roof (宀) over a young sprout (夭) — perhaps a sheltered, early growth, but its true sense remains a mystery.
For ヨウ, imagine a young sprout (夭) under a roof (宀) calling out 'Yo!' (ヨウ) to get attention.