1. To liquefy and purify the fatty tissue of something by applying heat to it. A noun or pronoun can be used between "render" and "down." You'll want to render the duck fat down so that it can be used for cooking later. You'll want to cook the meat on a low temperature for several hours so that you can render down the fat without burning it. After you finish carving the roast chicken, you should put the carcass in some simmering water to render it down.
2. To discuss, think about, or deal with something at its most essential or basic elements. A noun or pronoun can be used between "render" and "down." It's a complicated issue, to be sure, but it can really be rendered down to a single question—are you in favor of higher taxes or not? These big decisions can be really overwhelming, so I always try to render them down in more concrete, objective terms.
3. To convert one or more source files on a computer to a different media format. A noun or pronoun can be used between "render" and "down." Every time I render the different audio tracks down to a single WAV, they become shifted slightly out of sync. I filmed the raw footage at 60 frames per second, but it always renders down to 24 frames per second. What am I doing wrong?
render something down
1. Lit. to cook the fat out of something. Polly rendered the chicken fat down to a bit of golden grease that she would use in cooking a special dish. Jane rendered down the fat for use later. The cook rendered it down.
2. Fig. to reduce or simplify something to its essentials. Let's render this problem down to the considerations that are important to us. Can't we render down this matter into its essentials? Not all of this is important. Let's render it down.