Sports administrators that ruin ground covers: It's just not cricket! (6)
I believe the answer is:
unfair
'just not cricket' is the definition.
I don't understand how the remainder of the clue works.
(Other definitions for unfair that I've seen before include "Not just < dark" , "Not equitable or even-handed" , "Not cricket?" , "deceitful" , "Not equitable or blond" .)