noisy clack from chain area?

I have recently cleaned my chain, its a new DID one only has a few thousand on it if that..

The problem is there is a clack ,clack,clack from the chain area now with vibration as well. you can feel the clack through the footpegs.

Points to note: I think I can't adjust chains as I have always had 25mm play in the chain when I'm not sat on it and then its not slack play its forced movement, not hard though. The bloke in the shop says NO, slack movement is what the chain needs..! The chain also I think has a tight spot when you rotate the rear wheel on a paddock stand, the chain goes tighter and then looser?

I cannot reproduce the clack clack clack until I ride the damn thing and then I cant see whats happening. I have tried running it on the paddock stand and theres no clack clack clack.

So in essence- what the hell is wrong with it?

expensive trial and error for a new chain and sprocket set. its done 18k but tyhe new chain about 2-3 k and the sprockets look like new, I dont ride hard.

HELP..!!!!

Clean the chain with Parafin...properly.. adjust it... at the tightest point.. and you need slack movement... IE put your finger between the sprockets and push the chain up....

get it on a paddock stand and clean it. then go through it and wiggle each link to make sure its free moving. then lube it up then adjust it. if its clacking while your moving i would bet its a still link. get it sorted asap else it could mean it danages your chain