Letter to Sakellaropoulou's supporting commoner's figure of speech (9)

I believe the answer is:
prolepsis
'figure of speech' is the definition.
(thesaurus)
'letter to sakellaropoulou's supporting commoner's' is the wordplay.
I cannot quite understand how this works, but
'letter' could be 'psi' (psi is a kind of letter) and 'psi' is found within the answer.
'supporting' could be 'pro' (being pro something is supporting it) and 'pro' is found within the answer.
The remaining letters 'les' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
I've seen this clue in The Independent.
Want a hint initially instead of a full solution?
Install my app

Connecting...