I think its the three lletters TOP from TUBIFORM ONYX & PIDDLE that should be on the TOP line but not sure and have submitted a question myself. It seems very ARAUCARi-ISH. He isetting on a bit!
mrcroft is right about the first three letters of 1d, 2d and 3d. But also in clues T and Z, there are directional indicators suggesting they should be vertical, and in the first C, indicating it should be horizontal