No, neither one.  Here is a clause: "The man runs".  Here is what happens when I try to use it as a subject: *"The man runs surprises us."  No good.

Here is a noun: "man".  Here is what happens when I try to use it as a subject: *"Man runs."  No good.

For a subject, you need a noun phrase.  You can make a noun phrase from the noun "man" by adding a determiner: "The man runs."  You can also make a noun phrase from a clause by adding a complementizer: "That the man runs surprises us."

In some cases, nothing needs to be added to a noun to make a noun phrase which works as a subject: "Men run."  Nonetheless, "men" in this sentence is a noun phrase.