Athletic is taken over on Jan 1? (6)
I believe the answer is:
sinewy
'athletic' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for sinewy that I've seen before include "Muscular" , "Freshwater fish" , "Tough, fibrous" , "Toughly fibrous" , "Muscly; fibrous" .)