分析这句英语中的what

what引导的从句【what 】many might call the real work of his day在定语从句中作主语.
(注:when引导定语从句,修饰by nine)
而【what 】在从句中作call 的宾语,the real work of his day 作宾补,即:
many might call 【what 】the real work of his day
句意:他七点半起床,总是要到九点才吃完早饭,那时,许多人或许称作的他一天的真正工作才开始.