This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
黸 combines 黑 (black) with 盧, which likely contributes the sound. The exact historical development is uncertain.
The left side 黑 suggests blackness, and the right side 盧 is a complex shape. Picture a dark, sooty cauldron (盧) that leaves everything black.
For ロ, imagine a low, dark cloud rolling in: low -> ロ, and the cloud turns everything black like 黸.