What is Retain ?
Retain is (verb) 1. to keep something Please retain this invoice for tax purposes. One book especially retained my attention so I bought it. He managed to retain his composure in spite of being constantly heckled. 2. to retain a lawyer to act for you to agree with a lawyer that he will act for you, and to pay him or her a fee in advance
source: Easier English, Student Dictionary Upper Intermediate Level