If I have 1a correct, the last word (with a letter changed) is the definition. To be fair, I'd never have got it from the clue alone. 1d is probably the most straightforward in the Top left - child's word for a relative plus E. That might help with 1a.
I think I've got the grid filled now, but am stuck on the endgame. Only my last 9 extra letters seem to make any sense. And reading any of them backwards doesn't help. Any hints??