Old magistrates awfully idle, in the main, after retiring (7)

'old magistrates' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'awfully idle in the main after retiring' is the wordplay.
'awfully' is an anagram indicator.
'in the' indicates putting letters inside.
'main' becomes 'sea' (the main is an old name for the sea).
'after retiring' says the letters should be written in reverse (retire can mean to go back).
'sea' backwards is 'aes'.
'idle' with letters rearranged gives 'edil'.
'edil' inserted into 'aes' is 'AEDILES'.

Can you help me to learn more?