Sorry! The clue is: Holed material that's got brown on the outside (9)
The letters I had were t - e - o - n - d. If it is trepanned then my o is wrong. That comes from 3d: From left, I met calamities with radical new philosophy (11, 11) I had Diacritical colonialism which gave the o. Do you know what the answer should have been? And why?
Thanks.