This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
圢 combines 土 (earth) with 丁, which likely contributes a phonetic element. The exact historical development is uncertain.
The left side is earth 土, and the right side is 丁, which looks like a nail or a T-square. Picture leveling earth with a tool, but remember the meaning is uncertain.
For テイ, imagine using a T-square (丁) to level the earth (土): the T-square's shape suggests the sound "T" -> テイ.