You can create a Clear Structural Feature Action through an Activity Diagram or a Modeler pane.
To create a clear structural feature action through an activity diagram:
1. On the Activity Diagram toolbar, click the arrow in the split button that is to the right of the Accept Event Action button, click the > Clear Structural Feature Action button, and then on the Activity Diagram, click in free space or within an Activity Partition, Interruptible Activity Region or Structured Activity Node.
2. From the Select Object dialog, select the Attribute or Role that is to be the Linked Item, and then click OK.
3. Type the name of the Clear Structural Feature Action, and then press the Enter key.
Modeler creates the Clear Structural Feature Action and on it creates the default Object Pin input pin and the default Result Pin output pin.
To create a clear structural feature action through a Modeler pane:
1. In a Modeler pane, right-click the Activity or Structure Activity Node that is to own the Clear Structural Feature Action, point to New, point to Action Node, and then click Clear Structural Feature Action.
2. From the Select Object dialog, select the Attribute or Role that is to be the Linked Item, and then click OK.
3. Type the name of the Clear Structural Feature Action, and then press the Enter key.
Modeler creates the Clear Structural Feature Action and on it creates the default Object Pin input pin and the default Result Pin output pin.
Accept Event Action button, click the > 
Clear Structural Feature Action button, and then on the Activity Diagram, click in free space or within an Activity Partition, Interruptible Activity Region or Structured Activity Node.