Mail 15,198

[cracker222]

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?

[Captain2]

24 Essentially = middle letter of 'comMent'

[Mamyalynne]

Getting on - mature
Jumper - Roo
Spleen - Temper

[cracker222]

Grat help from you both - thanks. I learnt a lot from those.

[cracker222]

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