Fetching details from the dictionary...
reins; bridle
control; the reins (on)
馬の手綱を強く引いた。
I pulled hard on the horse's reins.
先生は生徒の手綱を緩めずに指導した。
The teacher guided the students with a firm hand.
その国の政治の手綱を握るのは数人の長老だった。
The political reins of that country were held by a handful of elders.