A fellow lives with handsome youth (6)
I believe the answer is:
adonis
'handsome youth' is the definition.
(I've seen this before)
'a fellow lives' is the wordplay.
'fellow' becomes 'don' (I've seen this before).
'lives' becomes 'is' ('be' can be a synonym of 'live').
'a'+'don'+'is'='ADONIS'
'with' is the link.
(Other definitions for adonis that I've seen before include "Aphrodite loved this beautiful youth" , "Beautiful (Greek) man" , "Legendary lover" , "lovely man" , "one deemed to be beautiful" .)