It's a noun phrase as the direct object of attempt . If you can replace the phrase with a noun, the phrase is nominal. If you can insert in order before the phrase and it still makes sense, it's adverbial.
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AnonymousHis ambition to become a teacher is something possible. (adjective modifying "ambition")No.
AnonymousIt is not easy to do this homework. (adverb modifying "easy")No.