This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
僜 combines 亻 (person) with 登, which likely contributes the sound. The exact historical development is uncertain.
A person 亻 beside 登, which suggests climbing or ascending. Without a known meaning, picture a person climbing a steep path, but remember the meaning is uncertain.
For トウ, imagine a person climbing a tall tower: tower -> トウ, and the person 亻 ascends 登.