We need a reference from your former employer.

employer 是由动词 employ（雇佣）加上后缀 -er 构成的名词，表示"雇佣者"，即"雇主"。 former 是形容词，意思是"以前的、从前的"，用来修饰 employer。 former employer 指"前雇主"，即之前雇佣过你的人或公司。