Group of clubs; distance (6)
I believe the answer is:
I believe this is a double definition.
'group of clubs' is the first definition.
(eg the Premier League)
'distance' is the second definition.
(Other definitions for league that I've seen before include "Combination of groups for a purpose, sports clubs perhaps" , "Group in football" , "sporting group" , "Old units of distance" , "Association - old measure of distance" .)