This question is being asked to see what your relationship is like with your current employer and, yet again, to better understand your motivations in wishing to leave them. Would you say that they led by example and were always willing to help out? Where they encouraging and empowering you to do your best work? When it comes to explaining details you didn't like, don't make them too negative. Leave out the names and personal details.
"My previous supervisor believed in getting in the weeds and being part of the action. If we were short handed he would answer phones, greet patients or help us file paperwork. It was nice to have the extra set of hands and have your supervisor want to help."