You can do this by "drawing" a line to each object within range and checking if it overlaps any solids. If you want a partial visibility, you can draw two lines instead - from the observer to edges of the target's bounding box to form a cone. If one line is obstructed but other is not, the target is partially visible.
Though overlapping and collision tests are CPU intensive. I believe a raytracing plugin would be a better option to reduce the overhead. There is Line of Sight plugin, for one.
If you want to simulate a Field of View effect - an overlay, a flickering torch or whatever - that is another story altogether. You want to draw a polygon that is limited by obstacles, this would be difficult to replicate in Construct.
It would be much easier if you had an "obstacle map" and used a certain pathfinding/flow algorithm to fill the area around player, then use this data to draw the Field of Vision.