I had similar issues with 5d and 6d, loge. I assumed the definition for 5d was “we’ll not submit”, and “slapdash” was the anagrind for both clues. Then “rewrites: one” becomes the anagrist. “by one, we would be fired” refers to the removal of “we” from the letters of “rewrites” to give the anagram “triers”, and after the ellipsis 6d is simply the clue for the second part of the anagrist.
But it’s all pretty messy, and the exclamation mark at the end of 6d might suggest John Henderson thought there was something much cleverer than that going on