A good answer depends on the volume of clippings you are working with and
how much you can spend on each.  I will pass on the effect of chemical
treatments on newsprint that is already aged, that is a little over my
head.  But based on what knowledge I do have, placing the clipping between
two sheets of Mylar that are then 90% sealed with tape or heat/pressure is
a easy, but expensive, way to deal with a limited number of clippings.