Installing a dimmer only where a light and fan switches exist
It looks like the wire wire in your switch box, is used as always hot or switched hot. You don't have neutral in there. I bet your power comes into the ceiling fan first, then to the switches. In this case, no, you can't use the smart switch....without re-doing the wiring at the ceiling and the box. You can do it with what wires you have, but the second switch would not work properly (you plan to remove it from the circuit anyway). 

You would need to switch wires in the ceiling so that "power" comes to the switch first, then switched to the fan. With the 3 wires you have, its easy to do. 

You will tie all whites together in the fan (new light) box, black on the fan (new light) to red and black from circuit breaker to black to switch (nothing hooked up in the fan box to the black wires(2) except just the two, 1 hot in and 1 hot out). At the switch, you will then have neutral (white), black (hot) and red (switched hot). From there you install the smart switch white(neutral) to neutral, black(hot) to hot and red to load. Best practice then is to use a 2 gang cover that has one side as a cover(blank).