The first one is unfortunately right (6)
I believe the answer is:
senior
'the first' is the definition.
(thesaurus)
'one is unfortunately right' is the wordplay.
'unfortunately' indicates an anagram.
'right' becomes 'r' (common abbreviation**).
'one'+'is'='oneis'
'oneis' is an anagram of 'senio'.
'senio'+'r'='SENIOR'
(Other definitions for senior that I've seen before include "More advanced in years or authority" , "Older or higher in standing" , "Elder person - higher in rank" , "Pupil in a higher form" , "Being old" .)