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

I feel, you will be the best person to decide that with the use cases you are describing. For deciding the actors you should find out who is external and is interacting with the use case manager, based on the context of the use case you are describing