crucible, melting pot
堝 centers on a container for melting or heating substances at high temperatures: a crucible or melting pot.
堝 combines 土 (earth, clay) with 咼, which likely contributes the sound. The character suggests a clay vessel used for melting, consistent with the crucible meaning.
The left side 土 (earth) represents the clay material, and the right side 咼 looks like a pot with a lid and a base. Picture a clay crucible used for melting metals.
For カ, imagine a car (カ) engine block being melted down in a huge crucible: car -> カ, and the intense heat turns the metal into liquid.