I've been keeping chickens for fifteen years, and never needed to clip any wings. My lowest outer fence is 5' tall, and for years, I kept the chickens separate from the garden with a moveable 3' roll of welded wire fencing. Then, last year, my new birds decided that 3' wasn't an impediment that they could respect. So I got a roll of 4'. They laughed. So I raised it to 5', and they said "OK, OK, we get it..." Then I added two new buff Orp pullets who had been raised in a flock of 100 in a hoop house. They weren't accustomed to close human contact, and one of them disappeared the day they arrived. Fortunately, we found her nearby, but were puzzled by how she could have gotten out. Then, the next day, she was gone again. We again checked the perimeter, and found it fine. So we concluded that she was flying over then fence, and clipped one wing. Problem solved. She's calmed down a bunch, and I don't expect to have to do it again after she moults. I'm also going to raise my outer fence to 6', just to be sure. We have a very healthy fox population in these parts...