Like James said, you can't tell by the picture what the gender of the clown is. In most cases it is correct to assume the larger one in a pair will be the female, but from what i've heard it's not always the case. Clowns are asexual, and if left by themselves for a long time will turn from sexless to male then to female and stay that way.
Is it by itself? and for how long? That would probably help to determine its gender.