If it is the 15 / 7.5 degree tele adapter it is straightforward to disassemble and clean. I tried to peel off the metal foil label but this only crinkled it and I couldn't refit the label. If I were to do it again I would slice the foil label along the plastic seam rather than try and peel it off. The label contains details of the exposure compensation to be set on the Profisix.
I also have the Profi Spot 1 / 5 / 10 degree attachment. This doesn't appear to be able to be disassembled by the average user. Mine is a little bit hazy but I think the haze is in the eyepiece as the meter readings I get are consistent with a couple of cameras I have with spot metering - Canon T90, F1-N.