I am sure crotchet will be correct, but I parsed 24a as
Sutorial (handicraft, sewing/cobbling etc) = hook(anagram indicator for) "tailors" + U*sed originally)
I am sure that the letters for the crossers will give you crotchet though!
Thanks Mac but I did also manage to parse Crotchet - I just find it strange that my first thoughts were a completely different answer and managed to parse it in a completely different way. I am sure that crotchet will be correct, especially as "sutorial" is an archaic word.