tight rein on, a

Idioms  

1. Strict control over, as in We told them to keep a tight rein on spending for the next year. This expression alludes to the narrow strap (rein) attached to a bit and used to control a horse's movements. Rein has been used to refer to any kind of restraint since the first half of the 1400s.

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Example Sentences

Scaramucci’s departure Monday is a good start, but Kelly will have to keep a tight rein on a White House staff that is used to few boundaries.

From Washington Post

It doesn't wander as far afield as many French comics and animated features, but that just lets it keep a tight rein on a story that makes flawless emotional sense.

From The Verge

But while the £6m summer signing from Wigan is anxious to return, Bruce will keep a tight rein on a man he wants to have ready for the start of the next campaign.

From The Guardian