One following US soccer's development (9)
I believe the answer is:
Here is my best explanation:
'one following' is the definition.
'us soccer's development' is the wordplay.
'development' indicates anagramming the letters.
'ussoccers' anagrammed gives 'SUCCESSOR'.
(Other definitions for successor that I've seen before include "One follows next in order", "One who follows another", "Person taking over from another", "one coming after you", "for one of the following people", "New leader", "Heir", "Follower (in post)", "One following another" and "He follows".)