This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
廥 combines 广 (building) with 會, which likely contributes sound and possibly the idea of gathering or storing. The exact historical development is uncertain.
The outer 广 suggests a building, and the inner 會 suggests gathering. Picture a storehouse where things are gathered and kept.
For カイ, imagine a storehouse by the sea (海, かい): the sea -> カイ, and the building stores gathered goods.