Is this Clause or falls under some other category

Question

a finding that has shocked most observers.

Full sentence: studies have shown that X is 60 percent of Y, a finding that has shocked most observers.

What is your opinion. Isn't it that the above is a clause?

This is what I know -

An appositive noun modifier, a type of modifier that NEVER appears in spoken language but that appears on the GMAT a lot. The reason is that, unlike relative pronouns such as 'which', these modifiers don't have to touch their referent. For instance: The general tried to get his troops to retreat before being surrounded, a strategy that ultimately failed. Exceptions - If you have an appositive modifier that's an abstract noun - such as "strategy", "figure", "statistic", "findings", "situation", "change", "difference", etc. - then such an appositive may be allowed to describe the entire situation described in the previous clause. For instance, the example I gave above with "a strategy..."Also, for further examples, see #59 and #79 in the purple verbal supplement OG book.

Answer 1

Your original sentence could be viewed as a modification of a similar sentence.

Studies have shown that X is 60 percent of Y, which is a finding that has shocked most observers.

For something to be a clause it needs to have a subject and a predicate. Therefore, "which is a finding that has shocked most observers" is clearly a clause. But, considering that in your sentence "which is" is omitted, which is our subject and predicate, it stops being a clause, and becomes a noun phrase (or an appositive).

Perhaps what causes some confusion is the clause "that has shocked most observers", but you have to consider that that clause is modifying "A finding", and therefore, it's just an adjective. If you look at the structure "a finding that has shocked most observers" as a whole, it's a noun + adjective, which is nothing worthy of calling that entire structure a clause (it still as a whole doesn't contain a subject and a predicate.)

A similar example of this structure noun + clause can be found on this website.

Upset by the bad call, the crowd cheered Robbie, a hot-tempered tennis player who charged the umpire and tried to crack the poor man's skull with a racket.

The entire bold part of that sentence is a noun phrase. (because the clauses coming after "a hot-tempered tennis player" just modify the "player". The entire structure on its own doesn't have necessary requirements to be a clause: a subject and a predicate)