This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蹎 combines 足 (foot) with 真, which likely contributes the sound. The exact historical development is uncertain.
The left side is 足 (foot), and the right side is 真 (truth/reality). Picture a foot stumbling on the truth—tripping over reality—to remember the kun-reading つまずく (to stumble).
For テン, imagine a foot (足) tripping over ten (テン) small obstacles: ten -> テン, and the foot stumbles.