How to: Hide Legend Items on the Chart
By default, any series added to a non-Shape chart will be added as an item in the legend. For pie, doughnut, funnel, and pyramid charts, any series added to the chart will add individual data points in the legend.
You can hide any item on the legend. When you hide a legend item, it will still appear in the chart. This is useful in situations where you do not want to show more information for a series that is added to the chart. For example, if you have added a calculated series like a moving average to the chart, you may want to hide this entry in the legend so that more information is only shown for the original series.
To hide an item from display in the legend
Right-click on the series you want to hide and select Series Properties.
Click Legend. Select the Do not show this series in a legend option.
You cannot hide a series for one group and not for the others. If you have added a field to the series group drop-zone, all series belonging to this group will be hidden.