Not a silly question.
And the noise seems much more like a "clunk" than a "click" to me.
A "clunk" being that something is hitting something else. A "click"being electrical in nature from a switch or other component.
In any case, update your post to include full system hardware specs and OS information. How old is the PC?
History of heavy use for gaming, video editing, or even bit-mining?
= = = =
Open the computer case and carefully use a cardboard tube or rolled up sheet of paper to "listen around" to both the PSU and the computer's components in general to pinpoint the source of the noise. What ever the noise is or sounds like.
Place one end of the tube to your ear and aim the other end of the tube as applicable. Have someone help so you do not hit any internal components. Take your time - no need to rush especially if the niose is constant.
After listening, power down and unplug the computer. User a bright flashlight to carefully inspect the area where the sound originates.
Look at the fan blades and any wires that may be free to move.
Look through the openings in the PSU but do not open the PSU. Nothing inside is repairable and attempting to do so can be dangerous.
See what you can find.