http://eldritchhorrorgame.wikia.com/wiki/Clairvoyance

What happens if you fail the roll? Do you have to do location encounter for the space you're at?

Yes, you would simply ignore what you were trying to do with the spell since you didn't pass. You do still have to resolve the flip side of the spell card, then you complete an encounter which would be for the space that you are on. Not the one that you were trying to reach out to with your mind.