This is the 300th most frequent Japanese word.
支部
Branch or chapter.
In this sentence, 支部 (shibu) refers to a branch office or a division of a company.
会社の東京支部で働いています。
I work at the Tokyo branch of the company.
In this instance, 支部 describes a subgroup of alumni specific to the university context.
彼は大学の卒業生支部の会長です。
He is the president of the university alumni branch.
Here, 支部 denotes regional branches that are part of an organization.