an-tee-tran-sub-stan-chee-uh-lay-shuh-nuh-list
Let's break it down:
* an-tee: Like the word "anti"
* tran-sub-stan-chee: The "tran" is pronounced like the word "train"
* uh-lay-shuh-nuh-list: Similar to "nationalist" but with a bit more emphasis on the "shuh"
Remember, it's a long word, so take your time and practice!