Sircrispin...
if you are entering 1a (12 letters) in 23a (8 letters) - you seem to have figured out the instruction.
I was hoping instruction will become clear with an example. For 12d, I have all the crossers that can yield only one 11 letter word, which has nothing to do with its clue.
So, I have not got the instruction. No problem with 21d, 28d
I guess i must get that answers to the 6 clues, before wondering where/how to enter them. Quite frustrating.