(idiomatic) to hold the key (to)

(idiomatic) to have something on (someone)

(Buddhism) head temple of a sect / (organizational) headquarters

good command of, full use of

to make excellent use of, to have a good command of

(historical) jiedushi (regional military governor in China during the Tang dynasty and the Five Dynasties and Ten Kingdoms period)

strengthens the prefixed adjective or adjectival noun

one who does the previous word's action: -ist, -er / (board games) counter for moves in shogi, go, etc.

hand / handicraft, skill, talent / one who does an action: -ist, -er / handwork

(childish) Alternative spelling of おてて (“hand”)