First, remove the pivot pin. Break the 6mm nut loose with a 10mm box end wrench. Take a flat blade screwdriver and remove that pivot pin. It should be smooth all the way around if you kept up greasing it with the drive chain and foot peg hinges and the like.
Next is to grease it, not WD it. Here is the trick. Since you wore out one side is that both are matched worn. So, if you spin the pivot down and then back it off a touch, you are cutting into new material. The 6mm nut will hold that staked where you set it, so the pivot now can run 1/2 on a new wound on the lever throw.
If you have the lever off, run grease into the backing under the lever pivots of the adjuster. Then move that plunger in without the lever in place. This might be the noise, since I told one guy at another site to do just this with the lube and his plunger was still making the noise. So, it is either or?
Tormenting the motorcycling community one post at a time