He could target research into clean energy technology, ending government initiatives and taking away research grants.
He could remove regulations on energy efficiency.
He could put giant tariffs on anything made in China that is used in clean energy production (like solar panels, batteries, and electronics).
He could make it harder to get approvals to install clean energy production, siding with NIMBYs who oppose solar, wind, and battery projects.
He could cut federal funding for public transit.
I don't know how much of that he would actually do, but in the past he has expressed support for a lot of it. So I think he will try to do some of it.
It's possible we have already reached a tipping point where the total cost of clean energy production and consumption is cheaper even without all of these subsidies and so on. If so, then the transition might continue anyway. But if so, I think it will still be a slower transition.