Yes. Sorry if it cofused any of you. I should have put 21dn not 21ac.
Having just come back from a walk in the rain while pondering the clue, I decided that electronic was just an "e".
If I've got 10ac right, I dont like the clue, because it is a "cliff" without the "permanent".
I found it easy getting started today, but then got stuck for a time with some very difficult clues.