A rugby player's carrying ball about (7)
I believe the answer is:
apropos
'about' is the definition.
(thesaurus)
'a rugby player's carrying ball' is the wordplay.
'rugby player's' becomes 'props' (I've seen this in other clues).
'carrying' indicates putting letters inside.
'ball' becomes 'o' (letter resembling a ball).
'props' going around 'o' is 'propos'.
'a'+'propos'='APROPOS'
(Other definitions for apropos that I've seen before include "With reference to, concerning" , "Regarding" , "To the point about poor spa" , "Concerned with" , "To the point, germane" .)