This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 盋 is uncertain. It visually combines 犮 and 皿, but the original meaning and component relationships are unclear.
The top part 犮 looks like a person pulling something, and the bottom 皿 is a dish. Imagine a person pulling a dish toward themselves, but the exact meaning is unclear.
For ハツ, imagine a person pulling a dish and exclaiming 'Hats off!' to the chef: hats -> ハツ.