He worked in a securities firm for ten years, gaining extensive experience in stockbroking.

stockbroking 是由 stock（股票）和 broker（经纪人）组合而成的复合词，加上后缀 -ing 构成名词形式，表示"股票经纪业务"或"证券经纪活动"。stock 指"股票、证券"，broker 指"经纪人、中介"，合起来指专门从事股票买卖中介的职业活动。