Tension the spring on levers

[HorTs]

Is there a way to tension the spring on a brake lever?

I have Ultegra 6800 and the left hand lever rattles. It need a little more tension to hold it still.

Any idea?

 

[Yellow Saddle]

You need to tension the brake cable and get rid of any play before it takes.

 

[andrew_s]

It's usually down to a sticky brake cable.
The spring in the brake caliper is what generally pulls the brake lever tight and stops it rattling.