Ford S Max Auxilary Belt Tensioner

Hi all. Just had a load of repairs done to our beloved S-Max and it passed its National Car Test, however I’m pretty sure a day or two later the Auxilary Belt Tensioner is on the way out. noticed a bit of a grumble at idle that goes away when accelerating. looked at the unit itself and can see it vibrating at idle.

I can’t get to a garage for a few days and ive one or two medium drives to do in the interim, how safe is this to drive for a week ?