Delete part of video clips

Click on the arrowed icon at the top right of the screen and then click Export File in the window that appears.

In the next window that appears click Next at the bottom right corner. You will then be asked to give the clip a name and specify where you want it saving . . . the Desktop is usually the most convenient place.

It is quite simply the bit rate.

The default iMovie setting gives a high bit rate which results in larger files.

Generally speaking the higher the bit rate the better the quality but I find that iMovie and Final Cut Pro tend to use higher bit rates than are really necessary.

Luckily you can adjust (lower) the bit rate to suit yourself.

In the share (export) window click on the Quality setting to disclose various options. Select Custom and you will see that the default for 1080p is 20 Mbps.

You can drag the slider to the left to reduce the bit rate . . . all the way to the left is 3.333 Mbps which will give you a file size of one sixth.

At 3.333 Mbps you may get digital artefacts with fast moving objects so you need to experiment and judge for yourself how much to move the slider.

You could put the section you want of the clip in the timeline and export it.

Delete the huge clip and import the short one you exported.

I don't think there is any other way like magically selecting the bit you want and deleting the rest . . . unfortunately that is not possible, as far as I know.

Yes. Share (export) the new clip from the timeline.

Delete the original clip.

Bring back your shared (exported) clip into the project.

How big is the original clip? It is usual to keep the complete clip unless it's an hour long and you only need a few seconds!

Unless the big clips are massive and filling up your hard drive you should just leave them alone.