Possible Engine Problem - Advice Needed

Hi Guys
My engine has developed a new noise and I wanted to get some advice before I take it to the garage. Can anyone help ??

Basically the engine produces a loud ticking noise when under engine braking. I do not use engine braking excessively, preferring to use the actual brakes almost 100%, so this is happening as I roll off the throttle or even as the engine slows while using the brake.
The noise does not occur when I pull the clutch in and coast, or when I pull the clutch in and brake so its definitely coming from the engine.
The noise itself is a rapid, metallic ticking, or tinking noise. Think empty tin can rolling down a hill.
Im riding a 2015 plate Tiger Sport with 20,000 on the clock. Regularly serviced and as I said I don't thrash it.

Noticed it worse in 2nd around 4-3000 revs, but maybe that's just because the wind noise is lower so I can hear it. Other than that the whole bike is sweet. Am I just being paranoid as the bike ages, or is this something more serious?
Just want to get some advice before I take it to some garage and get ripped off. Ill take any thoughts right now.
Thanks

 

Not a silly question at all - Im about mechanically minded as a duck.
The chain is a bit looser than it probably should be, not massively so, but might be enough I guess.

 

Thanks for the hints guys, I really appreciate it. The chain itself is in ok condition, I do clean and lube it regularly and the links are all free as best I can tell.
As to the frequency of the tinking, its not rhythmic, its all over the place, sometimes just three together, sometimes a whole series. Also doesn't happen every time I decelerate, but probably around 50% - as far as I can hear.

I think adding some chain tension is the first place I will check - just have to teach myself how to do that - but that's what YouTube is for ….right ?
If its that simple, Ill be very happy, but I was obviously paranoid it was coming from inside the engine.

 

Thanks Dave appreciate your experience. Not the best but a new chain is much more affordable than a new engine!