The simplest is to just disconnect and put a wire nut on each wire.

davidtay, thanks, but that will not work. In this case there is a switch that would be disconnected also. As it is, the power goes from the switch to the dimmer to the lights. I need the switch to work.

Ok, so the real issue is removing the dimmer.

To do that, find out which black wire goes from the switch to the dimmer.
Use a multimeter set to measure AC voltage to figure out which is the live wire to the dimmer. circuit is live at this point.
next, with the power cut, use the multimeter set to resistance measurements and the circuit is not energized. One of the wires - black or red will have a very low resistance to the switch controlling the dimmer.
It might be that the red wire runs all the way to the fixture and the black goes to the switch.

If so, the white wire from the dimmer can be removed and the black and red tied together.

If you're not confident, get an electrician.

davidtay, thanks. I have done some wiring over the decades, but so infrequently that I forget a lot and have to research each time. The dimmer has been removed. That old thing must weigh two pounds! Most of the weight is a transformer. I removed it because it had started to buzz.