Hi - I'm sorry I haven't repled, but I had to go out most of the day. I started this puzzle quite early, then just before I had to go out, came the EUREKA moment. I haven't finished it yet. As far as I have done, the unclued lights are proper words, and the letter that seems to be changed is the one that's actually entered on the grid. Worth noting - the word to be highlighted must consis of 8 letters, and I think there are only 3 8-letter words in the grid. Do you need a clue for the "eight of a kind?"