This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
埞 combines 土 (earth) with 定, which likely contributes the sound. The exact historical development is uncertain.
The left side is earth 土, and the right side is 定 (determine). Picture a determined patch of earth, but its meaning is unclear.
For テイ, imagine a tea (ティー) cup sitting on the earth: tea -> テイ, and the earth holds it steady.