This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 隟 is uncertain. It visually contains ⻖ (mound, hill) and 巢 (nest), but the original semantic and phonetic roles are unclear.
The left side ⻖ suggests a mound or hill, and the right side 巢 looks like a nest with a tree. Imagine a hidden gap in a hillside where a bird builds its nest, but the overall meaning remains uncertain.
For キャク, imagine a bird's nest tucked into a gap in a hill, and a quirky character named Kyaku peeking out: Kyaku -> キャク.