Controversy about contrary athlete (5)
I believe the answer is:
rower
'athlete' is the definition.
(I know that rower is a type of athlete)
'controversy about contrary' is the wordplay.
'controversy' becomes 'row' (both can mean a dispute).
'about' becomes 're' (regarding).
'contrary' says the letters should be written backwards.
're' backwards is 'er'.
'row'+'er'='ROWER'
(Other definitions for rower that I've seen before include "Person using 9" , "One who argues" , "Might one argue" , "One in eight, perhaps" , "Perhaps stroke" .)