This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
荂 combines 艹 (grass/plant) with 夸, but the exact historical development is uncertain. It may have originally referred to a type of plant or flower, but no clear meaning survives in modern usage.
The top 艹 suggests a plant, and the bottom 夸 might be seen as a large, showy bloom. Picture a plant with an exaggerated, boastful flower, but remember its meaning is unclear.
For カ, imagine a car (カ) driving past a field of these mysterious plants, their large flowers nodding in the breeze.