How Do I keep my mic from clipping?

If you're already clipping on the Input of your Audio Interface there is nothing Logic can do against that. Of course you can insert a Limiter to an Input object which you can create in your environment but that will only avoid the clipping of the Audio track you're recording to not the Signal Input in your Interface. If you're recording in 24 Bit you don't need to record at such high levels anyway. Also a good microphone singing technique could help you - soft notes near to the mic, loud ones a bit further away from the mic.

Which mic do you use, how is it connected to your mac? Since Logic allows you to record with 24bit resolution there is plenty of headroom and if you use an external audio interface reduce the gain and leave some (min 6dB) of headroom. After recording you can use a compressor plug-in to automatically adjust the volume levels of the track.

Cheers Eddie

How Do I keep my mic from clipping?

Turn the input on your mic-pre down.

Employ some "microphone technique" while singing, also called "working the mic". In other words, back off of the mic when you sing louder, move in a bit when you sing softer.