Does Alibaba provide a custom clearance if I import a product from Alibaba, or do I have to do it myself?

When you import goods the pesky clearance that you seek to avoid should actually be of prime importance to you.

Clearing goods through customs involves making a legal declaration to customs in YOUR name. YOU are responsible for every detail in that declaration and you pay any fines or penalties.

My wife once ordered some goods from Disney in the USA, we are in Canada, and the courier did the customs clearance. I was interested in that declaration because I am a customs broker, so I audited the declaration. On a couple of hundred dollars worth of goods I counted almost two thousand dollars in applicable fines for errors on the declaration. Including making a false declaration to avoid paying duties and taxes,

So if you like to live dangerously, let some unknown courier make your declaration. If on the other hand you like to sleep well at night, hire a professional customs broker. A license holding broker, member of the customs brokers association. someone who knows what they are doing.