You can delete individual objects by using the Delete method.
This example creates a lightweight polyline, then deletes it.
Sub Ch4_DeletePolyline()
' Create the polyline
Dim lwpolyObj As AcadLWPolyline
Dim vertices(0 To 5) As Double
vertices(0) = 2: vertices(1) = 4
vertices(2) = 4: vertices(3) = 2
vertices(4) = 6: vertices(5) = 4
Set lwpolyObj = ThisDrawing.ModelSpace. _
AddLightWeightPolyline(vertices)
ZoomAll
' Erase the polyline
lwpolyObj.Delete
ThisDrawing.Regen acActiveViewport
End Sub