What part of speech is the word straight in phrase it goes straight?

In the phrase "it goes straight", the word "straight" is an adverb.

Here's why:

* Adverbs modify verbs, adjectives, or other adverbs. In this case, "straight" modifies the verb "goes", telling us how it goes.

* Adverbs often answer questions like how, when, where, or to what extent. Here, "straight" answers the question "how does it go?"