Is the clicking noise coming from the compressor at the back?
Ok if you feel the compressor at the back is it hot to touch?
Ok not good news im afraid.
As the compressor is hot the motor inside it will have jammed up so this is why you hear a clicking noise. As the clicking noise is the relay on the side tripping out as the compressor isn't running.
For this fault you need to get a fridge engineer in as they will need to replace the compressor and regas it back up as this isn't a diy repair.
But this isn't going to be cheap to fix. As a new compressor fitted is roughly about the £200 mark so usually not worth fixing.
Sorry it isn't good news but if you need anymore info just get back to me.