I am tempted to define "journalism" as "a term of contempt applied by writers who are not read to writers who are".
最后的who are省略了read,和前面的who are not read里的read都是过去分词,构成被动语态.
apply A to B（把A用于B）是英语习语.Writers who are not read apply a term of contempt to writers who are (read）意思就是：那些没人读他们作品的作家把这个蔑称用到那些有人读他们作品的作家头上.