A forward's hogging ball? That's concerning (7)
I believe the answer is:
apropos
'concerning' is the definition.
(apropos means referring to or concerning a topic)
'a forward's hogging ball?' is the wordplay.
'forward's' becomes 'prop's' (both can mean a rugby player).
'hogging' is an insertion indicator.
'ball?' becomes 'o' (letter resembling a ball).
'props' placed around 'o' is 'propos'.
'a'+'propos'='APROPOS'
'that's' acts as a link.
(Other definitions for apropos that I've seen before include "fitting" , "With regard to" , "As regards" , "by the way" , "Concerned with" .)