What a weird one this is! I’ve managed most of it (though in quite a few cases I can’t parse the answers), but I’m still stuck on three:
52d: Emergency or upset thus besetting teacher (6)
I have - C - S - -
71a: Roughly holds sibling’s body (7)
I have C - A - S - - (the last letter also forms the last letter of 52d)
73a: Mostly when Jumbo appears easy, oddly is gratifying (5)
I have S - T - S
All help gratefully received!