Elder; first (6)
I believe the answer is:
senior
I believe this is a double definition.
'elder' is the first definition.
(similar in meaning)
'first' is the second definition.
(thesaurus)
(Other definitions for senior that I've seen before include "Superior - elder" , "Elder (of two)" , "Older in years or higher in rank" , "Elder person - higher in rank" , "High in rank" .)