a可以去掉,例如:

1、Part of the path had been washed away by the sea.部分小路已被海浪冲坏。

2、I'm putting by part of my wages every week to buy a bike.我每个星期把一部分工资存起来准备买辆自行车。

3、This unit is now an established part of the course.这个单元现在为本课程既定的一部分。