Hi.
Do you mean that water is constantly dribbling into the bowl? This is very likely a worn seal.
I've fixed this by replacing the rubber seal that sits at the bottom of the cistern.
You'll need to lift the flush mechanism out, to get to the seal.
Normally there are clips that hold the flush assembly and the cistern together. Get the assembly out, turn it upside down and you'll see the seal.
There are different sizes, so take it to your local hardware shop to get a matching replacement.
Very easy job to do.
Regards,
Adrian.