To delete a video effect, select the clip with the effect you want to delete. Then you can go to Clip>Video>Video Effects, or right-click the clip and select Video Effects, to open up the Add and Remove Effects window. The effects listed under “Displayed Effects” in the column on the right are the effects that have been applied to that clip. To remove an unwanted effect, click its name and hit the “Remove” button.
Effects can only be deleted one at a time.
You have another option for deleting effects if you are in Storyboard View. On your storyboard, the effects are displayed as little stars in the bottom left corner of each clip. Just click on the star and hit Delete to remove the effect. Be warned, though, that if there are multiple effects on the clip, doing this will delete them all. So use the other method if you just want to delete one effect and leave the others.