This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 辸 is uncertain. It combines the movement radical 辶 with 乃, but the original semantic and phonetic roles are unclear.
The movement radical 辶 suggests motion, and 乃 is a curved shape. Picture a winding path that goes somewhere, but the destination is unknown.
For ショウ, imagine a show being performed along a winding path: show -> ショウ, and the movement radical 辶 carries the performance forward.