Champion making an essential point about game (9)
I believe the answer is:
apologist
'champion' is the definition.
(both can mean someone who endorses another)
'an essential point about game' is the wordplay.
'an' becomes 'a'.
'essential point' becomes 'gist'.
'about' means one lot of letters go next to another.
'game' becomes 'polo' (polo is a kind of game).
'gist' put after 'polo' is 'pologist'.
'a'+'pologist'='APOLOGIST'
'making' is the link.
(Other definitions for apologist that I've seen before include "One who argues in favour of something controversial" , "Advocate" , "he puts up a defence" , "Person who argues to defend or justify some policy" , "Champion" .)