In a grammatical sense:
* Yes, a clause needs to have a subject and a verb. This is what makes it a clause and not just a phrase.
* It doesn't necessarily need to be a complete thought. A dependent clause, for example, relies on an independent clause to make sense. It acts like a modifier, providing extra information.
In a semantic sense:
* A clause can be grammatically correct but still not make sense logically. For example, "The purple elephant ate a green cloud" is grammatically correct, but it doesn't make sense in the real world.
* The meaning of a clause can be influenced by the context. For example, "He went to the store" might not make sense if we don't know who "he" is or what store he went to.
So, the answer is a bit nuanced:
* A clause needs to be grammatically correct, meaning it should have a subject and verb.
* However, it doesn't necessarily need to make sense logically or in the real world. It can still be grammatically correct even if it's nonsensical.
* The meaning of a clause can be clarified by context.
Let me know if you'd like to explore some specific examples!