There is not a command that will clear the config for a single port. For most commands you can simply place "no" in front of the command to remove it. So for dhcp l2relay you would run. no dhcp l2relayTo get rid of it.
  This might be an easy one but I can't figure out how to clear an individual port config for example, I want to delete this port config: interface ethernet 1/g1dhcp l2relayswitchport mode trunkswitchport trunk allowed vlan add 100,200,300 I want interface ethernet 1/g1 to be as though I never configured it :-) I looked a bit onine but nothing really turned up besides resetting it back to factory default.  I went into commands I used to set the port, "dhcp l2relay ?" but no joy as to a clue or tip on how to undo dhcp l2relay or wipe the individual port back to being unconfigured. Thanks in advance!  
Clearing a port config?