This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 冎 is uncertain. It appears as a component in characters like 骨 and 咼, but its independent origin is unclear.
The shape looks like an open frame with a small inner mark, but without a clear meaning, it is best remembered as a component in other kanji like 骨 (bone).
For カ, imagine a car (カ) frame that looks like the outer 冂 shape of 冎: car -> カ, and the frame is the kanji's outline.