衛 defense

I have to go and defend the orgy from The AYliens?? I dunno. . .

self-defense ★★★☆☆
自 (my own) + 衛 (defense) = 自衛 (self-defense)

self-defense - usually used in 自衛隊 (Japan's army, the Self-Defence Forces)

hygiene ★★☆☆☆
衛 (defense) + 生 (life / birth) = 衛生 (hygiene)

satellite ★☆☆☆☆
衛 (defense) + 星 (star) = 衛星 (satellite)

a bodyguard, an escort ☆☆☆☆☆
護 (defend) + 衛 (defense) = 護衛 (a bodyguard, an escort)