The advertisement was a want-ad about about cooks.

This question is incomplete, here´s the complete question.

The advertisement was a want-ad about cooks.

Is "want-ad" a subject, direct object, indirect object, predicate nominative, or the object of a proposition.

direct object

Explanation:

Direct objects are nouns or pronouns that receive the action taking place in the sentence. In reference to the verb o the sentence, the direct object answers the following questions: what? or whom?

On the other hand, the indirect object is a noun or pronoun that is being affected by the action. It´s someone or something that receives the direct object.

i don't know and i don't care .

i think the answer is second