Much harder than the usual Mail (for me anyway) but TAB's previous posts helped where needed. Still two I don't understand:
6d Getting on jumper first keeps spleen at about 20ºC (4,11) It's ROOM TEMPERATURE, but why?
24a Sort of a crass comment essentially (7) It's SARCASM, but where does the M come from?
I've tried 4 online dictionaries but cannot find essentially meaning central - although I have a vague inkling in my head of something like that usage. Must be a crosswordy thing