Elder Icelandic original in Norse translation (6)
I believe the answer is:
senior
'elder' is the definition.
(synonyms)
'icelandic original in norse translation' is the wordplay.
'original' says to take the initial letters.
'in' is an insertion indicator.
'translation' indicates an anagram.
The first letter of 'icelandic' is 'i'.
'norse' anagrammed gives 'senor'.
'i' inserted within 'senor' is 'SENIOR'.
(Other definitions for senior that I've seen before include "High in rank" , "Higher in rank or authority" , "Pupil in a higher form" , "Older in years or higher in rank" , "Elder person - higher in rank" .)