This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 畻 is uncertain. It visually combines 田 (field) with 龹 and 土 (earth), but the original semantic and phonetic roles are unclear.
With 田 (field) and 土 (earth), 畻 suggests something related to farmland, but its exact meaning is unclear.
For ショウ, imagine a farmer showing a field: show -> ショウ, and the field 田 is part of the kanji.