The link between setting goals and achievement is one of the

The link between setting goals and achievement is one of the clearest there is,with studies on everyone from woodworkers to CEOs showing that we concerntrate better,work longer,and do more if we set specific,measurable goals for ourselves.
这个‘there is‘ 在句中是什么用法?句子成分为何?

不管是你自己写的还是从哪个地方搞到的,句子结构确实挺复杂的,看起来好像还有点语法错误.句子可以翻译为：在设定目标和成果之间有很多联系,它们之中最明确的是,通过一个从木匠到CEOS的研究表明,在为我们自己设立一个清晰可实现的目标的情况下,我们必须要更加专注、花更多时间、（比别人）做的更多!
其中的there is不是短语“有什么”,这的there是名词不是副词,解释为它们,与clearest是一块的.变换之后是:The link between setting goals and achievement is （that）{one of the clearest there} is, 【with studies on everyone from woodworkers to CEOs showing that we concerntrate better, work longer, and do more if we set specific, measurable goals for ourselves.】