All of them turn up at the Royal Society! (6)

'all of them' is the definition.
I can't tell whether this definition defines the answer.

'turn up at the royal society' is the wordplay.
'turn' becomes 'come' (coming is a kind of turning).
'up' is a reversal indicator (in down clue: letters go upwards).
'at' means one lot of letters go next to another.
'the royal' becomes 'R' (abbreviation).
'society' becomes 's' (common abbreviation in names of organisations).
'r' put after 's' is 'sr'.
'sr' written backwards gives 'rs'.
'come'+'rs'='COMERS'

Can you help me to learn more?