Hmmm...If it's not leaking anything or making noise strangely it is not really a rover now is it? Does it make any worse noise if you are making a turn?

I had a similar problem erupt with my 94' rover. It sounded exactly like you described, but quickly developed clunking sounds and seizing if I was trying to turn.

Try checking out the front differential. It may be time to start shopping for a good used one or cheap rebuild. Replacing mine got rid of the noise and gave me at least some temporary peace of mind.

At first thoughts I thought it was the Vac pump ( common for ticking on the 300 when there worn ) , but the sound going when the clutch is depressed !!!!! - at a wild guess it could be a clutch fault ( broken damper spring ?? ) .

I had a clicking when the injection pump was pulling air(the banjo connection from fuel fiter was loose on the pipe)More noticeable under load.
To check if this is your fault take the return off the back of the injection pump(in the middle at the bottom,plus picks up injector leak off pipes)Fit a bit of clear tube and run it into a clean container.
Start engine and see what is coming out of the pipe-must be completely air free fuel-mine had micro bubbles.If you have any air chase back thru fuel system to find where it is getting in-there must be no air at all

Thanks for all the suggestions guys , the clicking has now been cured , the problem was that 2 exhaust manifold bolts had come loose and had been lost , allowing the gasket to “chitter” , so it wasn’t clicking after all ,( wot do I know ) ,
2 new bolts and a new gasket , problem sorted , ,,,,I can turn the radio down now ,,,,,,,,,,,,,,,,,,,,,,,,