How to set custom m4a format audio file as alarm tone on iPhone
First you'll need to add the audio file as a custom ringtone to your iPhone. For doing so, follow the instructions in the linked answer:


https://apple.stackexchange.com/a/1885/279727


Once you have the custom ringtone into your iPhone (you can check the same by going to Settings app → Sounds &amp; Haptics → Ringtone), you can also use it as an alarm tone in Clock app.