The flight feathers regrow every year, so clipping is an annual event. We have three drake mallards, and this year we are trying an experiment. We've clipped the alpha enough so that he can just kind of hover a few inches off the ground, and have left the other two unclipped. They never want to be too far from the alpha, so they are effectively clipped. (However, they are a little slow on the uptake, and not always the most precise of fliers, so I wouldn't recommend this strategy unless your yard has plenty of room.) We've chosen this strategy because a) it's really fun to watch them fly (again, if you have the room, and are fairly sure they won't end up in a neighbors yard, or worse yet, in the street), and b) we are in a wooded area, so lots of predators (a hawk has gone after them a few times), so allowing some flight seemed like a good idea.
Other than that, I'll reiterate what others have said. One duck is a sad, lonely duck. All drakes for us has been a little challenging. There's definitely a pecking order, with it being two against one. Having flexible caging options where the one can be separated, but still very close to and within sight of the other two, helps tremendously. They will get into this pattern where they cannot be next to each other, but they can't be out of each others sight either, enough so that they'd sooner sleep outside in subfreezing temperatures rather than be out of sight of each other in warm separate coops, even though they would tear into each other in the same coop. We now have separate coops with a mesh wall in between so they can see watch other, so now they always sleep inside.
Other than that, I'll reiterate what others have said. One duck is a sad, lonely duck. All drakes for us has been a little challenging. There's definitely a pecking order, with it being two against one. Having flexible caging options where the one can be separated, but still very close to and within sight of the other two, helps tremendously. They will get into this pattern where they cannot be next to each other, but they can't be out of each others sight either, enough so that they'd sooner sleep outside in subfreezing temperatures rather than be out of sight of each other in warm separate coops, even though they would tear into each other in the same coop. We now have separate coops with a mesh wall in between so they can see watch other, so now they always sleep inside.