His cattle deployed for sport (9)
I believe the answer is:
athletics
'sport' is the definition.
(synonyms)
'his cattle deployed' is the wordplay.
'deployed' indicates an anagram.
'his'+'cattle'='hiscattle'
'hiscattle' anagrammed gives 'ATHLETICS'.
'for' acts as a link.
(Other definitions for athletics that I've seen before include "Lithe acts (anag)" , "Partly track" , "Olympic sports" , "Sports -- cheat list (anag)" , "Lithe acts performed in physical sports" .)