I am new to drawing use case and writing use case descriptions.

I have an Actor called User , an abstract usecase called Work Type and another use case called Manager. The usecase Manager has a generalized relationship with the Work Type use case.

I'm now writing the use case description for Manager use case. And what is the initiating Actor for this use case. Is it the Actor User ? or doesn't it have an initiating Actor ?

Note: I only want to know the initiating Actor for the use case Manager