cleverjo and malone
Thanks -it was about "contranyms" although that word is not in my old Chambers.
But join and connect are synonyms of buckle and antonyms of cleave.
Similar for break and split.
They were poor examples.
It was clearly not an interesting one as there was no thread for a week, possible the first EV with no thread?
Interestingly "Hawk" the compiler managed to get several hawk references in the clues and grid.