What does on a china mean?

"On a china" is not a common phrase in English. It's possible that you're thinking of one of these phrases:

* "On a China": This could be a misspelling of "on a china plate" or "on a china cabinet". These phrases refer to placing something on a decorative dish or in a cabinet made of porcelain or china.

* "On a China sea": This could be a misspelling of "on the China Sea", a marginal sea of the western Pacific Ocean.

Could you please provide more context? For example:

* What was the full sentence?

* What was the topic of conversation?

* Where did you hear this phrase?

This will help me understand what you're asking and give you a more accurate answer.