The jeweler set a large pearl into the brooch.

Literal

Jewel-craftsman [topic-は] that brooch [into-に] large pearl [object-を] fitted-in

宝石細工師 is a three-part compound: 宝石 (jewel) + 細工 (crafting) + 師 (practitioner). はめ込む is a compound verb: はめる (to fit/insert) + 込む (into) = to set/embed something. 真珠 (しんじゅ) = pearl.