There's a trick we use with college essay writing that often comes in handy with unfocused fiction scenes, too. This has to do with focusing the material so that it is coherent free of distractions, well-paced and relevant. Sometimes, we have scenes that seem to flitter around from idea to idea, and even though it all seems to flow smoothly enough in a line-by-line way, the sum is less than the parts.
In a college essay, when a paper bounces around like this, we ask students to reverse-outline the paper. That is, they take the finished paper and go through it paragraph by paragraph to identify the main topic of each paragraph. This requires them to evaluate each paragraph individually and decide what it is about. Is every sentence in the paragraph related to the main topic? Are there two or more topics covered in a single paragraph? Are the same topics addressed in multiple paragraphs? These are the things we evaluate as we reverse outline, and frequently, the process of asking these questions is enough to show the students how to rearrange the existing parts, snip the irrelevant bits, and end up with a stronger paper.
In fiction, of course, we don't have this methodical, one-topic-per-paragraph approach to organization. Nevertheless, a similar process of reverse outlining can help a lot with an unfocused scene. Most scenes have one main conflict, just as most academic paragraphs have one topic. Most scenes will contain some supporting material, just as most academic paragraphs will, and in either case, it's not a bad idea to double check whether this supporting material actually supports the main idea. In fact, if you've ever completed a scene chart, you've already done a bit of reverse outlining with fiction. In a scene chart, we identify things like the main conflict, the main goal of each character, any complications or obstacles, and the like. This lets us understand what the scene is ABOUT the same way a reverse outline can help a college student get a grip on the paper they've already written.
So that's the first step for this sort of refocusing process -- identify the main conflicts, goals, and obstacles. You have to know what the scene is supposed to be about before you can measure whether it meets those goals. Once you've figured that out, then, you need to look at the scene to see whether you hit the target. A quick way to check this involves a highlighter -- either a highlighter marker and paper, or the highlighter tool in your word processor. Just go through and highlight every line that is directly related to the main conflict, the main character goals, and the main obstacles. If it's not directly related to those things, don't highlight it.
If the scene is wildly out of focus, you'll have a lot of plain text with no highlighting. But this doesn't always mean those plain bits should be cut. The scene might have sub-goals. Or the scene might foreshadow something that will happen later. Maybe there's a red herring. These things should legitimately be included in some scenes, so they can stay. Highlight them, too, but you might want to use a different color for these essential but secondary bits.
Some of you might be tempted to highlight pieces on the grounds that they contain "character development." Resist that temptation. The main action of the scene -- conflicts, goals, obstacles, plus a bit of description to ground the reader in the story's reality -- are where you should be developing the characters. Not in explanatory asides. If it doesn't tie in to the action of the scene, chances are that it doesn't belong in the scene at all. Ditto clever banter unrelated to the conflict, lovingly rendered descriptive passages, and anything else that was super fun to write but is only muddling the scene now. Don't highlight this stuff.
You should be left with a good chunk of important highlighted pieces and a scattering of secondary highlighted pieces. Read the scene through, skipping anything that isn't highlighted. These are the bones of the scene. This is what the scene is ABOUT. You might need to rearrange these pieces or write some brief transitions to smooth out the scene, but in most cases, you won't need anything except the highlighted pieces in order to make a solid, focused, relevant, readable scene.