stiffen
tighten **
tighten up
constrain *

The race tightened up in the final weeks of the campaign.

So the state has no had to tighten up the law to cut the cost.

When things tightened up, I never tried to play big.

This is something that really needs to be tightened up.

Not very much, but enough to make me tighten up again.

We will, quite simply, have to tighten things up in these areas.

Now the rules are being tightened up, and that is only right.

So maybe that might tighten them up a little bit.

He tightened up a little but let me hold it.

It really started to tighten up in the second half.