Champion in utter darkness (6)
I believe the answer is:
knight
'champion' is the definition.
(I have seen 'Heroic champion' mean 'knight' so perhaps 'champion' could also mean 'knight')
'utter darkness' is the wordplay.
'utter' shows a homophone (sound like) (I've seen 'uttered' mean this).
'darkness' becomes 'night' (night is a kind of darkness).
'night' is a homophone of 'KNIGHT'.
'in' is the link.
(Other definitions for knight that I've seen before include "nobleman" , "soldier" , "board member" , "Rank below baronet" , "- - errant" .)