What job is the noun clause doing in this sentence? a polite guest will eat whatever is served.

The noun clause 'whatever is served' is functioning as  a direct object. You can check this by replacing the noun clause with the word 'something'. That is one way to check that a part of the sentence is a direct object. Also, if you check the meaning of the verb "eat" in a dictionary, you will notice it usually needs an object to complete its meaning.

racism is the belief in the superiority of one race over another, which often results in discrimination and prejudice towards people based on their race or ethnicity. the use of the term "racism" does not easily fall under a single definition.

explanation:

the group received an extra pound of butter for christmas.

the annex was delighted to hear that we'll all be receiving an extra quarter pound of butter for christmas.