[slijin]

Assuming you want to make a funnel-esque shape, you'll need to do loft twice if you want to use loft to do this. First, you have to loft (using the join option) the outer rim of the face of the cylinder adjacent to the circle to the circle. Then, you have to draw the inner rim of the mouth of the funnel on that circle, then loft it (using the cut option) to the inner rim of the face of the cylinder you previously lofted from (which requires selecting the sketch by navigating to it in the sidebar).

The much easier way would be to create a midplane of the cylinder parallel to the Y-Z plane, use that to sketch the cross-section of the funnel, then revolve it around the cylinder's central axis.