Morning headwreck ,definitions I found for covert ,,are ,( a covering that serves to conceal or shelter ) or (covered over ,private, hid secred, disguised.)
Then again ,cavern,(a large cave),cavort,(play boisterously) Would also fit in.But out of those three I thought covert was the best.There is probably many more words that would fit in .Think this one is going to be like the "cane/able one from a few weeks ago I think!