Siamese kitten clear whitish eye discharge?

I would bathe it just with warm water and see how it goes, is there any chance your cat could have had a fight? and maybe he has been caught in the eye. Or he could have an infection but for now I'd bathe it and if there is no improvement then you'll have to take him back, but in the meantime you could call the vet and explain the problem, if he thinks its nothing least it will settle your mind.