Hi Mpart,
I did find a troubleshooting tips page on the adapter:
Apple Portables: Troubleshooting MagSafe adapters
https://support.apple.com/en-us/HT203207And also passed the question onto Hubby and this is what he says:
Okay, first off, unplug it and leave it unplugged. Burn marks mean there's a short in the system. Continued shorting could cause permanent damage to the system and could cause a fire. Not something you want to mess with.
Regardless of whether the system is under warranty or not, you may need to have it looked at to determine whether the charger or the connector is causing the short and either have it repaired or replaced.
It's normal for a laptop brick to get warm. It's not normal for a connection point to burn the port.
MrsFlynn