He’s an expert on the smart set (7)
I believe the answer is:
stylist
'expert on the smart set' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'he's an' is the wordplay.
I cannot quite understand how this works, but
'an' could be 'i' (Roman numeral for one) and 'i' is found within the answer.
'he' could be 'ty' and 'ty' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for stylist that I've seen before include "One who shapes or designs, say hair-do" , "An expert in elegance, say hairdresser" , "Elegant writer" , "Designer of fashionable clothing" , "One who creates elegance as of clothes or design" .)