This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
爀 combines 火 (fire) with 赫 (bright, radiant). The exact historical development is uncertain, but it likely relates to firelight or brightness.
Fire 火 beside radiant brightness 赫 suggests intense firelight, but the exact meaning is unclear.
For カク, imagine a bright fire crackling with a sharp 'kaku' sound: kaku -> カク, as the flames roar.