public void Clip( 
   Layer layer,
   long oid,
   Geometry clippingGeometry,
   ClipMode clipMode
)

// Clips a feature to the specified polygon.
await QueuedTask.Run(() =>
{
  var clipFeatures = new EditOperation() { Name = "Clip Features" };
  clipFeatures.Clip(featureLayer, objectId, clipPolygon, ClipMode.PreserveArea);
  //Execute to execute the operation
  //Must be called within QueuedTask.Run
  if (!clipFeatures.IsEmpty)
  {
    //Execute and ExecuteAsync will return true if the operation was successful and false if not
    var result = clipFeatures.Execute();
    //or use async flavor
    //await clipFeatures.ExecuteAsync();
  }
});