rein
noun
uk/reɪn/ usthe reins [ plural ]
power and control of a business or other activity:
These are the councillors who hold the reins of power.
He handed the reins to his successor.
I am retiring, and someone else can take over the reins.
free rein
the freedom to do what you want to do:
have free rein We were told we had free rein on questions of design.
give sb/sth free rein (to do sth) She was given free rein to make all the changes she wanted.
give/allow sth full rein (also give/allow full rein to sth)
to allow something to happen freely and completely:
This is a post which will give your talents full rein.
It's a task that requires you to allow full rein to your imagination.
keep a tight rein on sth
to control something very carefully:
We need to keep a tight rein on the advertising budget.