Number of balls thrown, grey (8)
I believe the answer is:
overcast
'grey' is the definition.
(thesaurus)
'number of balls thrown' is the wordplay.
'number of balls' becomes 'over' (cricket term).
'thrown' becomes 'cast' (I've seen this in another clue).
'over'+'cast'='OVERCAST'
(Other definitions for overcast that I've seen before include "not entirely fair" , "The sky covered by dark clouds" , "Not very bright" , "(Of skies) grey" , "(Of sky) cloudy, dull" .)