Degree (5)
'degree' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for grade that I've seen before include "Degree" , "School mark" , "Particular level of rank, quality, etc" , "one of the entertainment moguls" , "Rank or status" .)
(Other definitions for nth that I've seen before include "To the -- degree" , "Umpteenth" .)