Clash-of-clans – How to get revenge on someone if they are in the clan

No, you can only 'Revenge' on a normal attack.

Which means that if someone attacked you, and you Revenge attacked them, they cannot attack you back through Revenge. They won't have this option in their message box.

The only way for them to attack you back would be if they find you again on normal attacks, but that's rather unlikely since your trophy levels would now be different and there are so many players around the world.

Note that a clan member cannot Revenge for another of their members.

You can revenge anyone in your defence log unless you have already revenged them or they revenged you. Then the option will not be shown. Also, you have to try to revenge when the player is offline or unshielded or else you will not be able to attack them.

Items will not remain in your defence log based on time, there seems to be a limit of 27 items which are cycled out as you get attacked again.