Satchel, it’s adapted for sport (9)
I believe the answer is:
athletics
'sport' is the definition.
('athletics' can be a synonym of 'sport')
'satchel it's adapted' is the wordplay.
'adapted' is an anagram indicator.
'satchel'+'it'='satchelit'
'satchelit' is an anagram of 'ATHLETICS'.
'for' is the link.
(Other definitions for athletics that I've seen before include "Physical sports for trained competitors" , "Oldham and Charlton?" , "Sports - his cattle (anag)" , "Partly track" , "Lithe acts observed in sporting contests" .)