Could you guys tell me what “put a clock on it” means?
the context:

If we had the necklace it would make things a whole lot easier for your witch, but since we're doing this the hard way, let's put a clock on it, shall we?
(He puts the clock. There's a buzzer sound when the clock appears on the board)
Klaus: 20 minutes. If Bonnie hasn't found a solution by then, I want you to feed again. Only this time, I want you to feed on Elena. You know you want to.

Could you guys tell me what “put a clock on it” means and make two sentences with it? thx!

Question

Could you guys tell me what “put a clock on it” means?
the context:

If we had the necklace it would make things a whole lot easier for your witch, but since we're doing this the hard way, let's put a clock on it, shall we?
(He puts the clock. There's a buzzer sound when the clock appears on the board)
Klaus: 20 minutes. If Bonnie hasn't found a solution by then, I want you to feed again. Only this time, I want you to feed on Elena. You know you want to.

Could you guys tell me what “put a clock on it” means and make two sentences with it? thx!

Answer

put a clock on it = give it a time limit
In this case they set the clock to 20 minutes.

Answer

"Put a clock on it" is not a phrase we use in English.  It is hard to tell what is going on in your story.  It seems that someone is wanting to "time" something....see how much time it takes to find a solution to a problem.  There are several bad mistakes in this writing.  I think you did not spell "watch" correctly, and you said "witch".  There is an error in saying someone is going to "feed on Elena.  I believe "put a clock on it" means set an alarm on a clock, or check to see how long it takes for something to happen, but this paragraph has many errors.