Right to drink retsina, wrong to show self-control (9)
I believe the answer is:
restraint
'self-control' is the definition.
(thesaurus)
'right to drink retsina wrong' is the wordplay.
'right' becomes 'rt'.
'to drink' indicates putting letters inside.
'wrong' indicates an anagram.
'retsina' is an anagram of 'estrain'.
'rt' enclosing 'estrain' is 'RESTRAINT'.
'to show' is the link.
(Other definitions for restraint that I've seen before include "Check" , "Start rain as an impediment" , "Curb" , "Reserve" , "Limiting device" .)