Just as important as safety is providing adequate food for the chick. You need to locate it in a spot where the bigger ones can't bully the chick while it's trying to eat.
If a chick is bullied away from the feeder, this can result in the older ones "teaching"the chick that it doesn't want to eat, and it won't get enough nutrition for full development. Worst case would be it could actually starve.
What I do is install a little "panic room" in the corner of the pen with openings that only the chick will fit through. It will quickly learn to run there for safety and food. Once it attains close to full size, it will be able to fend for itself.
Right now I have three ten-week olds that aren't able to get enough food during the day, being chased and bullied away from all the feeders. So I've taken to offering them food three times a day in the safety of the coop without the others breathing down their necks. Believe me when I tell you they take full advantage of these special feedings and pork up!
When you have different ages merged together, it requires constant vigilance, and yes, even meddling.