Learn Italian: Il vicolo è buio, ma l'uomo ne scappa per la salvezza. - The alley is dark, but the man escapes from there for safety.

Ne is a locative pronoun that means from that place or out of it. It replaces dal vicolo (from the alley). While you could grammatically say scappa da lì, using ne is much more natural and common in Italian to express movement away from a place you just mentioned.

Doesn't ne usually mean 'of it' or 'some of them'? How can I tell it means 'from there' here?

You are right that the partitive ne (meaning some of it) is often taught first! However, ne also acts as a location word. You can tell the difference by looking at the verb. Verbs of movement away from a place, like scappare (to escape), uscire (to go out), or tornare (to return), will trigger this 'from there' meaning.

Could we use the location pronoun ci here instead?

No, because ci and ne indicate different directions. Ci means 'to there' or 'in there' (movement toward a place or staying in a place). Because the man is escaping away from the alley, you must use ne, which specifically means 'from there'.

Why does Italian use the article la in per la salvezza when English just says 'for safety'?

In Italian, abstract nouns like salvezza (safety, salvation) generally require a definite article. So, while we say 'for safety' in English, Italian literally says 'for the safety'.