Sportsman's father not taking sides, accepting foul shot (7)
I believe the answer is:
athlete
'sportsman's' is the definition.
(type of sportsman)
'father not taking sides accepting foul shot' is the wordplay.
'not taking sides' indicates the central letters (the external or side letters are removed).
'accepting' means one lot of letters goes inside another.
'foul shot' becomes 'let' (tennis term).
The central letters of 'father' are 'athe'.
'athe' placed around 'let' is 'ATHLETE'.
(Other definitions for athlete that I've seen before include "gymnast, maybe" , "Holmes, perhaps" , "Sporty type" , "Bolt perhaps" , "fine physical specimen" .)