A measure of class (6)
I believe the answer is:
league
This clue is a double definition.
'a measure' is the first definition.
(league is a kind of measure)
'class' is the second definition.
(thesaurus)
'of' is the link.
(Other definitions for league that I've seen before include "Former measure, approx. three miles" , "Alliance, association" , "Association of teams for competition" , "Competing group of clubs" , "Group of sports clubs; about three miles" .)