sound of setting up a koto
揁 is a rare kanji whose given meaning is the sound of setting up a koto. Its standalone meaning is narrow and tied to a specific traditional context; treat it as a character for that sound or action.
揁 combines 扌 (hand) with 貞, which likely contributes the sound. The exact historical development is uncertain, and the character is rare.
The hand radical 扌 beside 貞 suggests a hand adjusting or setting something. Imagine a hand carefully tuning a koto, producing the characteristic sound.
For テイ, picture a hand setting up a koto on a tea table: tea -> テイ, and the hand makes the sound of setting it up.