It is normal to hear a clicking sound while your refrigerator is running. This sound could be coming from the defrost timer if your appliance is a no-frost model or from the ice making function if your refrigerator is equipped with an ice-maker.
If you have noticed an increase in the internal temperature along with the clicking sound, your appliance’s compressor may be overheating and the clicking sound is the sound of it turning off. The problem may be related to condenser coils.
The condenser is responsible for releasing the heat your appliance produces. Its wires cannot perform efficiently if they are covered with dirt or dust. Unplug your appliance and locate the coils at the back of your appliance. You can clean the coils with a gentle brush or the brush attachment of your vacuum provided it’s set to a low suction power. Do not use damp cloths or towels when cleaning the condenser coils.
If your appliance is not operating normally while making this noise, consider contacting an authorised service agent.