Hi
I think this is the sort of thing you have in mind... Old film type image with borders..

To deal with this, click the FX button on the sequence line and after clicking the Green cross on the effects pane select the "Crop" effect from the list.
This will place a rectangle on the CLIP PREVIEW pane.
If you want to keep the AR fixed to a particular value then select it from the options in the "Restraint" box. e.g. select 4:3 for old analogue video or super 8 format. Note: there will be black border on the resulting VP clip unless the original image is 16:9.
Drag the sides of the rectangle so as to outline the part of the clip you wish to be seen. i.e to crop off the fuzzy border and round corners..
Close the effects pane.
The video will now play without the fuzzy edge or round corners....but will not fill the frame.

The resulting clips plays without fuzzy border but will not fill the frame.
If however you have cropped with the AR set at 16:9 you can (although you will have lost some of the image) enlarge the frame to fill the screen using the "Zoom" or "Scale" effect. (Scale is a bit phaffy so I would use Zoom)
So to add the Zoom effect to the crop you have done.....
Click FX and the green cross to select "Zoom" The zoom panel will come up over the Crop panel.
Set the red cursor line to the start of the clip and the Restraint box to 16:9 (Same as your original Crop option)
Drag the sides of the rectangle appearing on the CLIP PREVIEW pane so as to outline your cropped image. (Undock the preview pane to see it more clearly)
Click each of the keyline buttons and then the small green cross on the keyframe window. This sets the first keyframe.
Slide the red cursor line to the end of the clip and then drag the rectangle to the right to the end of the clip and centre it again.
Click the small green cross once more to set the end keyframe.
Now close the effects pane.
The image (16:9) will now fill the complete frame.

When played the clip will now show the 16:9 cropped image zoomed in full frame.
Nat