Before we finalize the contract, we should talk it through with our legal advisor.

talk 是动词，意思是"谈话、讨论"。 it 是代词，指代前文提到的"合同"。 through 在这里是副词，表示"彻底地、完整地"。 talk it through 是一个固定短语，意思是"彻底讨论、详细商议"，强调把问题或事项从头到尾完整地讨论清楚。