这句用了隐喻，展开说明了前句中的护卫者徇私舞弊的不必要性：定时适度高标准供应+无经济匮乏的精神折磨。一句话，物质享受都备好了，护卫者只管尽职工作，为民为国谋福利。

For they will be protected from want; the necessities and modest luxuries of a noble life will be theirs in regular provision, without the searing and wrinkling care of economic worry.
因为他们将免于匮乏之苦，贵族生活所需的必需品与适当的奢侈品，会稳定地供给他们，而不必承受经济忧虑所带来的灼人且催人衰老的折磨。

细节解析

1、want：the state or condition of being poor匮乏
Machinery that gives abundance has left us in want.《名人演讲综合》
在句中，“want”不表示需要，而表示物质的匮乏， 与“be protected from”一起，表示护卫者“免受贫困之苦”。
2、sear: to burn and damage the surface of (something) with strong and sudden heat烧掉……的表面
Meanwhile, I've got a hot pan to sear off some figs.《美食家基地》
在句中，用“Sear”来比喻经济忧虑带来的强烈、尖锐、即时的痛苦，就如被烫到一样。
3、wrinkle: to develop wrinkles起皱
Then the old man's face wrinkled itself slowly into a new expression.《秘密花园》
在句中，用“wrinkle”来比喻经济忧虑带来的长期的、缓慢的褶皱，就如皮肤或纸张慢慢起皱。这种担忧会在脸上、心理上和生活中留下痕迹，使人衰老。

所在段落

The Story of Philosophy《哲学的故事》第1章Plato第7节VI. The Political Solution第6段第2句：

This arrangement will make it unprofitable, as well as dangerous, for the guardians to rule as a clique seeking the good of their class than that of the community as a whole. For they will be protected from want; the necessities and modest luxuries of a noble life will be theirs in regular provision, without the searing and wrinkling care of economic worry. But by the same token they will be precluded from cupidity and sordid ambitions; they will always have just so much of the world's goods, and no more; they will be like physicians establishing, and themselves accepting, a dietary for a nation. They will eat together, like consecrated men; they will sleep together, like soldiers sworn to simplicity. "Friends should have all things in common," as Pythagoras used to say (Laws 807). So the authority of the guardians will be sterilized, and their power made poison less; their sole reward will be honor and the sense of service to the group. And they will be such men as from the beginning have deliberately connected to so materially limited a career; and such men as at the end of their stern training will have learned to value the high repute of the statesman above the crass emoluments of the office-seeking politicians or the "economic man." At their coming the battles of party politics will be no more.
浙江大学译本： 因为护卫官受保护而不被欲求困扰；他们维持贵族生活的日常所需和适当的奢侈品是定时定量供给的，因而也没有经济窘迫的顾虑。

上句见：Day459