Additional qualification for sportsperson (5)
I believe the answer is:
rider
This clue is a double definition.
'additional qualification' is the first definition.
(qualification or condition in a contract)
'sportsperson' is the second definition.
(eg horse rider)
'for' acts as a link.
(Other definitions for rider that I've seen before include "Clause added to a legal document" , "One in the saddle" , "Clause appended to a legislative bill" , "Person on horse" , "Horseman or add-on verdict by jury" .)