The sophisticated fellow's property (3)
I believe the answer is:
his
'the sophisticated fellow's' is the definition.
'his' can be an answer for 'fellow's' (belonging to a man). I am not certain of the 'the sophisticated' bit.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for his that I've seen before include "That man's" , "To - Coy Mistress (Marvell)" , "It belongs to him" , "Belonging to that man" , "that chap's" .)