Onegin, for one, in central Greece throttling upper-class dope (6)
I believe the answer is:
eugene
'onegin' is the definition.
(novelist Eugene Onegin)
'one in central greece throttling upper-class dope' is the wordplay.
'one in' indicates putting letters inside.
'central' says to take the centre.
'throttling' means one lot of letters goes inside another.
'upper-class' becomes 'u' (similar in meaning).
'dope' becomes 'gen' (both can mean information).
The middle letters of 'greece' are 'ee'.
'ee' placed around 'u' is 'eue'.
'eue' enclosing 'gen' is 'EUGENE'.
'for' is the link.
(Other definitions for eugene that I've seen before include "Great American playwright . . . . . . O'Neill" , "opera, but only first half" , ". . . . . . Onegin (Tchaikovsky) (6)" , "- - Onedin" , "Dramatist...... O'Neill wrote 'The Iceman Cometh'" .)