If he spends most of his time playing about in the way that he used to as a child, he will go hungry.

参考译文:如果他像小时候那样把大部分时间都花在到处玩耍上，他将会挨饿的。

从句:If he spends most of his time playing about in the way that he used to as a child,

主句:he will go hungry

从句语法结构分析如下

If【连词】//  he【主语】//  spends 【谓语动词】// most of his time【宾语】//  playing about in the way that he used to as a child【状语】// 

备注(1):从句使用结构:spend+时间段+(in) doing sth在做某事上花费时间，介词in可以省略。

备注(2):playing about in the way that he used to as a child现在分词短语作状语

备注(3):about为副词作地点状语修饰现在分词playing，about意思“到处/各处”

备注(4):in the way that he used to as a child为介词短语作方式状语修饰现在分词短语playing about.

备注(5):that he used to as a child为定语从句作定语修饰名词way

类似于以上句子:spend+时间段+(in) doing sth结构例句如下

Engineers spend much time and energy developing brilliant solutions.

工程师们花费很多时间和精力来开发完美的解决方案。

Businessmen spend enormous amounts advertising their products.

商人们花费巨额资金为自己的商品做广告。

The company has spent thousands of pounds updating their computer systems.

公司花了几千英镑更新计算机系统。

Most of her life was spent in caring for others.她大半辈子的时间都用来照顾别人了。