I came across this sentence and am not sure whether it is grammatical. It looks like the clause "a second essential function vision serves" functions as a subject and is embedded into the outer clause.
[[A second essential function vision serves] is to facilitate major changes.]
The embedded clause has its inner structure similar to a noun clause, i.e. "what vision serves" but it starts with a noun phrase "a second essential function" which is not a pronoun.
My question is, can a clause like "a second essential function vision serves" function as a subject or object in a sentence?
Thanks a lot.