You can delete chat if you are in a game or not (using android or I Pad).
1. Go to chat box
2. Touch the chat box you want to delete, box will become shaded, white message box will appear - "Delete".
3. Touch "Delete"
4. Next message, Delete Message, This action cannot be undone, CANCEL YES
5. Touch YES. Message in that chat box will be deleted on that device.
5. You must delete each individual chat, one at a time, on each device you've used to chat.