1rein 
/ˈreɪn/ noun
plural reins /ˈreɪn/ noun [count] 1 : a strap that is fastened to a device (called a bridle) placed on the head of an animal (such as a horse) and that is used to guide and control the animal — usually plural ▪ The rider pulled on the reins to stop his horse. — see picture at horse 2 a : the ability to limit or control something
▪ We need to keep a rein on our spending. [=we need to limit/control our spending] ▪ He has people working for him, but he has/keeps a tight rein on every part of the process.
b : the power to guide or control someone or something — usually plural ▪ They held the reins of government/power. [=they controlled the government] ▪ She handed the reins of the company to her successor. = She handed over the reins of the company to her successor. ▪ The President-elect will officially take the reins [=take control] in January.
▪ We need to keep a rein on our spending. [=we need to limit/control our spending] ▪ He has people working for him, but he has/keeps a tight rein on every part of the process.
b : the power to guide or control someone or something — usually plural ▪ They held the reins of government/power. [=they controlled the government] ▪ She handed the reins of the company to her successor. = She handed over the reins of the company to her successor. ▪ The President-elect will officially take the reins [=take control] in January.
free/full rein
: the opportunity to act freely
▪ The studio gave the director free rein [=complete control] over the movie. ▪ Give full rein to your imagination.
▪ The studio gave the director free rein [=complete control] over the movie. ▪ Give full rein to your imagination.
