No, Evil is correct. What he is referring to is a bolted circular clamp the same diameter of the steerer tube, which serves the same function that the stem does when it is tightened. Actually, the real purpose of a "compresssion spacer" is to allow the the stem to be moved up the steerer tube w/o needing a lot of regular spacers. Still, trying to adjust a headset properly w/o a topcap with either a star nut or compression plug is difficult at best, so his decision to simply buy another start nut is the correct one.