This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 隑 is uncertain. It combines ⻖ (mound, hill) with 豈, but the original meaning and component function are unclear.
With no clear meaning, picture a forgotten mound (⻖) beside an old musical stand (豈) — a relic whose purpose is lost.
For カイ, imagine a forgotten mound that was once a quay (kai) by the water: kai -> カイ, though the kanji's meaning is uncertain.