Athlete arranged a ransom (7)
I believe the answer is:
oarsman
'athlete' is the definition.
(I know that oarsman is a type of athlete)
'arranged a ransom' is the wordplay.
'arranged' indicates an anagram.
'a'+'ransom'='aransom'
'aransom' with letters rearranged gives 'OARSMAN'.
(Other definitions for oarsman that I've seen before include "It's bordered by Libya and France" , "Male rower" , "One in a row" , "galley slave, say" , "One in an eight?" .)