Photographers know that what makes an image significant or striking is very often the way it is framed, and for this reason they frequently crop the borders of their pictures after they are taken. Exactly the same thing can be said about the mental picture which your essay is aiming to convey to the reader: what will make this picture effective will be the way you have set its boundaries by defining the problem.
At the level of essay structure, this framing function will be performed by the introduction and conclusion to your essay. Your introduction will be especially important to the framing of your essay, since here you have to anticipate the needs of your reader by setting out the direction your essay is going to take, a context of which you will later have to remind your reader through signposting.
You will also have to think about framing by means of cues and connecting words at the more detailed level of sentences and paragraphs. You can establish a framing context which will greatly help your reader by paying attention to the kind of hierarchy of clauses within a sentence, and of sentences within a paragraph, which outlining represents.