You may notice leaves at one corner while the rest of the gutter is difficult to see. Describe that corner, the nearest downpipe and the side of the house. A safe wide photograph helps place the detail in the building layout. Mention trees near the property without estimating the contents of a channel you cannot see. There is no need to climb or pull out material before speaking to us.
If clearance has been done before, include when and which sections were covered. That history can help explain the present problem. It is not a guarantee that every run is still clear or that new debris has the same cause as the earlier blockage.