Everyman, ultimately terrified, rises before the Royal Society in quaking fits (7)

'quaking fits' is the definition.
'dithers' can be an answer for 'quaking' (thesaurus). I'm unsure of the 'fits' bit.

'everyman ultimately terrified rises before the royal society' is the wordplay.
'everyman' becomes 'i' (where 'Everyman' is the setter of the crossword).
'ultimately' indicates one should take the final letters.
'rises' is a reversal indicator.
'before' is a charade indicator (letters next to each other).
'royal society' becomes 'RS'.
The final letter of 'terrified' is 'd'.
'i'+'d'='id'
'id' in reverse letter order is 'di'.
'di'+'the'+'rs'='DITHERS'

'in' is the link.

Can you help me to learn more?