In my other post I was really talking about using a click track for ensemble work. Not really necessary for solo harp but you may want to use one anyway depending on what you are doing.
Click track bleed can be a real pain when working with acoustic instruments. I use Direct Sound Extreme Isolation headphones which are excellent for minimizing these problems. The trouble is, as the bit that goes over your ear is a bit hefty, I find myself having to tilt my head to the left a little to stop it from knocking into the harp!
Also I’ve found that if you an EQ the click so as some of the high frequencies are rolled off then there is less chance of it bleeding through.