Two lots of Greek letters containing a rhetorical device (8)
I believe the answer is:
chiasmus
'rhetorical device' is the definition.
(chiasmus is a kind of rhetorical device)
'two lots of greek letters containing a' is the wordplay.
'two lots of' becomes 'chis' (I can't explain this - if you can you should believe this answer much more).
'greek letters' becomes 'mus' (I've seen this in another clue).
'containing' means one lot of letters goes inside another.
'chis'+'mus'='chismus'
'chismus' placed around 'a' is 'CHIASMUS'.
Can you help me to learn more?
(Another definition for chiasmus that I've seen is " rhetorical device".)