KANJI - JLPT 1 KYUU

1) イン, 2) かく・す, 3) かく・し, 4) かく・れる - conceal, hide

隠れん坊 kakuren bou - hide and seek (game)
隠密 on mitsu - spy
隠し味 kakushi aji - hidden flavor
雲隠れ kumo gakure - disappearing (like a ninja into a cloud)
隠語 in go - secret language