It means that its not really fair. The game of cricket is considered a gentlemans game and it should be all fair and above board. Anything that "isnt cricket" means its not really fair.
A piece of history, that! (I see another bowler's just been done for ball-tampering, and the sound of Aussie sledging will soon ring across the land.) I think golf is the only sport these days that really insists on the highest standards of honesty.
I take cricket most seriously!!! Just because the foreigners can't abide by the rules! JOKING!!! I'm not a bloomin racist or a xenophobic so don't start (or mention Athers' gravel!)