Athlete is snubbed by this competitor (7)
I believe the answer is:
thrower
'athlete' is the definition.
'snubbed by this competitor' is the wordplay.
'snubbed by' becomes 'th' (I am not sure about this - if you are sure you should believe this answer much more).
'this competitor' becomes 'rower'.
'th'+'rower'='THROWER'
'is' acts as a link.
(Other definitions for thrower that I've seen before include "who offends the umpire?" , "shyer" , "One who intentionally loses" , "tosser" , "participant in discus event?" .)