it的指代,what从句

it的指代,what从句
Since Bruce Li first one-inch punched his way onto Western screens,the definition of what it means to be a martial arts movie star has been evolving.自从李小龙踏入西方影幕第一步,作为一个武术电影明星的定义已有所发展.这事我从2008年4月23号的21世纪报上抄的一句话,想重点提问“the definition of what it means to be a martial arts movie star”这个部分,请问it指代谁?what在从句中充当什么成分?以及这句话的确切意思?请高手从语法角度透彻的分析一下,

1.首先你要明白mean的用法.
（1）一般用法：Her only son means a lot to her.就a lot提问：What does her only son mean to her?
（2）形式主语用法：It means a new beginning to go to university.It代替to go to university做形式主语.就a new beginning提问：What does it mean to go to university?此题刚好用的就是这一点.
2.此题的解释.
（1）the definition has been evolving.是句子的主干.翻译：这个定义已经改变了.
（2）what it means to be a martial arts movie star 肯定做of介词的宾语,是个宾语从句.而what又做means的宾语.翻译：作为一位武打演员意味着什么的定义.
（3）it代替to be a martial arts movie star做宾语从句的形式主语.
（4）整句翻译：自从李小龙首次打进西方影坛,作为一位武打演员意味着什么的定义已经改变了.