clip polygon by length of line

Clearly define the problem and an explanation will come to you. What do you mean by ‘cut’ and ‘length’.

Splitting the polygon with the line you have shown won’t work as-is with a line on area overlayer because the orange line doesn’t extend fully across the polygon, it doesn’t cut the area. You could extend the line, but that would be cutting using a different length.

Do you want the end result to be a donut (like a paper cut enclosed within a sheet of paper), or two polygons?

Or do you want this part:
 

Because then you could simply use a Bufferer with “End Cap Style: None” and then a Clipper

Hi ​@ctredinnick , many thanks for the feedback , i have adjusted the question and added more information about what i am trying to achieve.

I am looking for a result with 3 polygons based on my example. 

Hi ​@max_h ,thanks for the feedback, i had thought of that but the buffer distance is not the same for all the polygons, in my example i have used a standard rectangle which a bufferer and a clipper can do the job.

As you’re clipping it, you can just buffer by 999999, not the most elegant, I know, but depending on your data that should work.
If it isnt that simple, many outliers/ curved polygons instead of rectangles etc. an excerpt of your data would help