He'll use it as a bargaining tactic. That's what he does. Unless your country is able to manufacture every commodity at home your economy is reliant to some extent on imports. If you make these more expensive to buy, prices go up for consumers and businesses, wages go down and inflation takes off. Trump knows this, but he'll impose tariffs long enough to create a panic in Europe and then he'll put on his best beaming smile and say, OK guys, you don't want the tariff's, lets do a deal.
The only country he really wants to shut out of America is China, and in that the UK and Europe should support him.
Trump tariffs could work greatly in the UK's favour if our adolescent student activist government had the brains to secure a trade deal. But they won't, because it's Trump.
But if he uses defence spending as a lever to slacken tariffs (which is highly likely), Reeves' budget will unravel faster than a knitted vest. Another win for the UK.
It's going to be interesting and potentially quite entertaining to watch.