As Hurdy says - probably the cam chain tensioner.
But ... I had (probably) the same noise just before Christmas, and not wanting a large bill just then, I put some Wynns valve lifter cleaner in. I ran it for a hundred miles or so and the noise went.
I then dropped the sump, put a new oil pick up pipe on ( the old one was not very dirty ), cleaned out the sump, new filter, oil and the noise has not come back. Fingers crossed!
If it does, then yes, will have to get the cam chain and tensioner done.
Could be worth trying first.