This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
隚 combines ⻖ (mound/dam) with 堂 (hall). The exact historical development is uncertain, but it likely originally referred to a raised earthen structure or foundation.
The left side ⻖ suggests an earthen mound or dam, and the right side 堂 suggests a hall or building. Picture a raised earthen platform that serves as the foundation for a hall.
For トウ, imagine a tall earthen foundation supporting a grand hall: the tall foundation cues トウ, like the English word 'tall' but with a long vowel.