This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蹞 combines 足 (foot) with 頃, but the exact historical development and original meaning are uncertain.
The foot radical 足 suggests a meaning related to walking or stepping, but no clear meaning is available. Think of it as a mysterious foot-related kanji.
For キ, imagine a key (キー) unlocking the mystery of this rare foot kanji: key -> キ.