Old folk finally see ex-PM with prison visiting (9)

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

'finally see ex-pm with prison visiting' is the wordplay.
'finally' says to take the final letters.
'ex pm' becomes 'truss' (former UK prime minister Liz Truss. I am not sure about the 'ex' bit.).
'with' says to put letters next to each other.
'prison' becomes 'can' (the can is American slang for prison).
'visiting' indicates putting letters inside.
The last letter of 'see' is 'e'.
'e'+'truss'='etruss'
'etruss' placed around 'can' is 'ETRUSCANS'.

Can you help me to learn more?