All 11 Uses of

render
in
The Screwtape Letters

we thus aggravate the female's chronic horror of growing old ... and render her less willing and less able to bear children.
Chpt 20 *

render = make

It is, no doubt, impossible to prevent his praying for his mother, but we have means of rendering the prayers innocuous.†
Chpt 3 *

And it is also to be noted that the Trough sexuality is subtly different in quality from that of the Peak—much less likely to lead to the milk and water phenomenon which the humans call "being in love", much more easily drawn into perversions, much less contaminated by those generous and imaginative and even spiritual concomitants which often render human sexuality so disappointing.†
Chpt 9

As the uneasiness and his reluctance to face it cut him off more and more from all real happiness, and as habit renders the pleasures of vanity and excitement and flippancy at once less pleasant and harder to forgo (for that is what habit fortunately does to a pleasure) you will find that anything or nothing is sufficient to attract his wandering attention.†
Chpt 12 *

The Enemy will also try to render real in the patient's mind a doctrine which they all profess but find it difficult to bring home to their feelings—the doctrine that they did not create themselves, that their talents were given them, and that they might as well be proud of the colour of their hair.†
Chpt 14

Ever since our Father's first great victory, we have rendered the former very difficult to them.†
Chpt 18

We have done this through the poets and novelists by persuading he humans that a curious, and usually short-lived, experience which they call "being in love" is the only respectable ground for marriage; that marriage can, and ought to, render this excitement permanent; and that a marriage which does not do so is no longer binding.†
Chpt 18

There must be several young women in your patient's neighbourhood who would render the Christian life intensely difficult to him if only you could persuade him to marry one of them.†
Chpt 19

While it lasts you have your chance to foment the problems in secret and render them chronic.†
Chpt 26

A great human philosopher nearly let our secret out when he said that where Virtue is concerned "Experience is the mother of illusion"; but thanks to a change in Fashion, and also, of course, to the Historical Point of View, we have largely rendered his book innocuous.†
Chpt 28

Definitions:

(1) (render as in: rendered service or a verdict)
to give or supply something
(2) (render as in: rendered her unconscious)
to make or cause to become
(3) (render as in: rendered interpretation)
to portray or create something in a particular way; or to interpret, translate, or extract from
The exact meaning of this sense of render depends upon its context. For example:
- "Each artist will render a different interpretation when painting a portrait." -- create in a particular way
- "A Supreme Court judge may render his own interpretation of the Constitution." -- interpret in a particular way
- "The computer you are using, rendered this page from software instructions." -- created through interpretation
- "A graph is rendered from the underlying data." -- made
- "Fat can be rendered (extracted) by cooking meat slowly." -- extracted from
(4) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

A comprehensive dictionary will have more specialized definitions of render.