سلام Shirts, such as t-shirts, are very often used to show some form colloquial slang. Proper grammar doesn't play a role in those instances. The expression that you describe indicates some type of sexual connotation, so it seems. Paul alluded to that as well. A@@ can be used as slang to refer to sex. I reiterate, "can be used" in a slang way. It doesn't only mean sex. In my opinion, the shirt that you saw does mean it.

It could mean 2 things if it is on a shirt: 1. I want more than just a@@. Or 2. I want something, but not a@@.

Hello! It seems like there might be a mistake or misunderstanding in the phrase you provided. "Just won't want ass" doesn't appear to have a clear or meaningful interpretation in English. It's possible there's a typo or miscommunication in the text. If there's more context or if you have the correct wording, feel free to share it, and I'll do my best to help you understand its meaning.

Yes of course