This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
覴 is a rare character combining 登 and 見. The exact historical development is uncertain, but it likely follows a phono-semantic pattern where 登 contributes sound and 見 contributes the idea of seeing.
The left side 登 suggests climbing or ascending, and the right side 見 is an eye. Imagine climbing up to get a better view, staring intently from a high place.
For トウ, picture climbing a tall tower (タワー) to stare down: tower -> トウ, and from the top you gaze intently.