Italia, I was not on an arrival, and atc did not give me any descent, just cleared for the approach, while I was at FL 80. So am I correct to wait until within the 25 mile MSA and then leave FL 80?
I don't have the charts right now so I can't say for sure but if you are cleared for the approach you do not need further clearance to descend. You do still need to follow the minimum altitudes that are on the approach chart and the other IFR charts. If you're already at the lowest altitude for your position then you can't descend.
Cleared for arrival = cleared for the path dictated on chart, do not descend without clearance
Cleared for approach = descent at your discretion while adhering to the altitude restrictions on your "path" and cleared to fly the arrival "path".