cover, shade, mantle, capsize, be ruined
蔽 centers on covering or concealing something from view, like a shade or mantle. The less common senses of capsizing or being ruined extend from the idea of being overwhelmed or covered over by disaster.
蔽 combines 艹 (grass) with 敝, which likely contributes the sound and the idea of covering or concealing. The exact historical development of 敝 is uncertain, but the overall structure suggests hiding something under grass or vegetation.
Grass (艹) covers over the lower part (敝), like a thick mantle of vegetation hiding what lies beneath. This covering can shade, conceal, or even capsize and ruin what is hidden.
For ヘイ, imagine a heavy hay bale covering the grass: hay -> ヘイ, and the hay shades everything underneath.
concealment; hiding; covering up; suppression
shielding; sheltering; screening; shading; masking
cover; concealment; masking; screening
information hiding
bunker; covered trench; dugout
shelter; cover; screen; shield; obstruction; defilade
suppressor
(creating) a cover-up
cryptic coloration (colouration); camouflage