Athlete was a moron, sadly (9)
I believe the answer is:
oarswoman
'athlete' is the definition.
'was a moron sadly' is the wordplay.
'sadly' is an anagram indicator.
'was'+'a'+'moron'='wasamoron'
'wasamoron' with letters rearranged gives 'OARSWOMAN'.
(Other definitions for oarswoman that I've seen before include "Rower" , "River user" , "Girl having paddle" .)