Behind European athlete, one that came first (10)
I believe the answer is:
forerunner
'one that came first' is the definition.
(a forerunner comes before others)
'behind european athlete' is the wordplay.
'behind' becomes 'for' (I've seen this in other clues).
'european' becomes 'E' (abbreviation e.g. EU).
'athlete' becomes 'runner' (type of athlete).
'for'+'e'+'runner'='FORERUNNER'
(Other definitions for forerunner that I've seen before include "one coming ahead" , "Precursor" .)