Cutting & Trimming Clips in Final Cut Pro

I'm pressing command B to make both cuts to the clip, then selecting the section between these cuts and hitting the delete key, above my return key. This cuts the section out fine but leaves a gap where it used to be., I don't want this, I want all clips that follow this to automatically slide left to make up the space, so I don't have to do it manually. I'm sure that this is an extremely simple thing to fix but it's driving me crazy.

Correct. I reset my preferences and opened the project back up, still the same. I've since deleted that project and started again, new project, and hey presto, everything is working how it should.

It would be good to know actually what had happened, maybe I pressed something I shouldn't. But in any case, It's taken up enough of my time today, I'll just crack on from scratch.

Thanks anyway guys.

As you may have guessed, I'm new to FC so can't tell you if I was cutting on the 'primary story line' or not as I don't know what that is. I was cutting as you've pictured above, though.

The other thing I noticed was that I had to select the clip before making the cut marks. If I didn't select it first, the cut marks would be made instead to the MP3 audio file that I had running underneath my clips by default.

Now that I've started a new project, I've got my clips and audio again beneath, but i can cut as normal by hovering over my clips rather than having to actually select them first. And, as I mentioned before, the gap created by making a cut is automatically filled with the remaining clip.

Thanks, but I'm still getting the same result whether using either tool.