Here is one way to tackle that. One can go to the Table of Contents in the ArcMap document being used and make a copy of the layer there, then display the full layer in the map and use a reduced one in the legend.
So to start, make a copy of the layer in the Table of Contents. Note that this is all being done in the Table of Contents of the final map layout (we are not modifying or copying the actually file on disk).
Then for that copy, go into the Properties while in the Table of Contents and then in the legend symbology area delete the item you don't want to appear (in your case populated place). While you are in the Properties, it is helpful to add something to the layer name so you can distinguish it from the original. For example, if the layer name is PlacesOfInterest, I would modify it to be PlacesOfInterestLegend. Then check off the display of this layer in the Table of Contents (but leave the original layer checked on), so only the original layer is being displayed.
Finally, to finish this off, go to your legend box in the layout, right-click on it, then for the layers list add in the one you modified. So in my example PlacesOfInterestLegend. Remove from the list the original layer. Note that you may need to set the Property in the legend box that controls display of layers that are not turned on, as this may suppress the legend layer you just made.
Chris Donohue, GISP
