Learn French: Il va se perdre parce qu'il n'a aucune boussole. - He is going to get lost because he has no compass.

The word aucune means 'no' or 'not a single'. The structure ne... aucun(e) is a complete negative pair that replaces ne... pas. You cannot use pas and aucune together.

Why do we use aucune instead of aucun here?

Aucun acts as an adjective, so it has to match the gender of the noun it modifies. Since boussole (compass) is a feminine noun, we use the feminine form aucune.

Normally we would say il n'a pas de boussole. Why isn't there a de before boussole in this sentence?

While pas requires de when talking about zero quantity (meaning 'not any'), aucune translates directly to 'no' or 'not a single'. It is an adjective that attaches straight to the noun, so the word de is not needed.

Why does the first part use se perdre instead of just perdre?

Perdre on its own means to lose an object (like losing a compass or your keys). When a person 'gets lost', French uses the reflexive verb se perdre (literally 'to lose oneself').