Favouring English athlete: one came first (10)
I believe the answer is:
forerunner
'one came first' is the definition.
(a forerunner comes before other people)
'favouring english athlete' is the wordplay.
'favouring' becomes 'for' (I've seen this before).
'english' becomes 'E' (abbreviation).
'athlete' becomes 'runner' (runner is a kind of athlete).
'for'+'e'+'runner'='FORERUNNER'
(Other definitions for forerunner that I've seen before include "one coming ahead" , "Precursor" .)