No, not quite. — What you’d do is just find some sort unique element that is current surrounding the area you want to change.
So, for example, say you have markup that looks like this:
Well to target this featured-image-wrapper specifically, you’d do this:
.whatever .featured-image-wrapper { ... }
This is what CSS means, “Cascading Stylesheets” — Meaning that because this is more specific, it will take precedence.