cover, conceal
掩 centers on hiding something from view: covering it up or concealing it so it cannot be seen.
掩 combines 扌 (hand) with 奄, which likely contributes the sound and the idea of covering or concealing.
The hand 扌 beside 奄 suggests a hand covering something: imagine a hand placed over an object to conceal it from sight.
For エン, picture a hand covering the end of a box to hide its contents: end -> エン, and the hand conceals what is inside.
cover; concealment; masking; screening
emplacement; bunker; shelter
bunker; shelter
cover trench
sneak attack (by a small group); surprise attack
cover(ing)
bunker; covered trench; dugout
covering force
direct escort; direct cover; combat air patrol; CAP