No, the night would still be dark with a star at that apparent magnitude. The sun as seen from earth is -26.74 and "Sun as seen from Earth (about 400,000 times brighter than mean full moon)." That is what it would take to light up the sky that much. A full moon is -12.29 and that does not make the night significantly brighter. You can see your way around in the dark but that is about all. -6 for our star is much smaller than even that so it would not have as serious effect as you are supposing. About the worst of it is that it could possibly be visible during the day given the right conditions.

Here's the wiki link I'm pulling my suppositions from. From what I understand the ratings are not linear, but logarithmic? Which I think puts them on a curve meaning the meaning of the numbers changes more than they would seem to indicate.