“当职员”可以翻译为“work as a clerk” 或者 “be a clerk” 。
“work as a clerk” 强调从事职员这份工作的行为动作；
“be a clerk” 则侧重于表达“是职员”这样一种身份状态。
例如：
He works as a clerk in a big company.（他在一家大公司当职员。 ）
She has been a clerk for five years.（她当职员已经五年了。 ）