This expression literally means 'to remove one's marble from the game'. It is not an expression related to the game of marbles, though. "Tir so kanet dan zwe" means: to find a trick or an excuse to get out of it.
For example, in a group discussion, if you notice that one of you is trying to avoid the conversation or change the subject, you can say "li pe rod tir so kanet dan zwe".
Another example: If your children have done something wrong and one of them accuses the other, he or she will find a way to "tir so kanet dan zwe".
