Una corazonada permite acertar.

Because corazonada is a feminine singular noun, so it takes the feminine singular article una.

• una corazonada = a hunch
• la corazonada = the hunch

A lot of Spanish nouns ending in -ada are feminine, and corazonada is one of them.

Because the stress pattern changes.

• corazón needs an accent mark because the stress falls on the last syllable: co-ra-ZÓN
• corazonada is stressed naturally on the second-to-last syllable: co-ra-zo-NA-da

Since corazonada follows normal Spanish stress rules, no written accent is needed.

Permite is the third-person singular present of permitir.

The subject is una corazonada, which is singular, so the verb must also be singular:

• una corazonada permite

If the subject were plural, the verb would change:

• Las corazonadas permiten acertar.

Because after permitir, Spanish commonly uses permitir + infinitive.

So:

• permite acertar = allows/enables someone to get it right

This is very common in Spanish:

• permite entender = allows you to understand
• permite aprender = allows you to learn

Here, acertar means to get it right, to guess correctly, or to be correct.

Depending on context, acertar can have slightly different meanings, for example:

• acertar la respuesta = to get the answer right
• acertar con la decisión = to make the right decision
• acertar on its own = to be right / guess right

In this sentence, it means that a hunch helps you arrive at the correct answer or conclusion.

Because acertar can be used without a direct object when the meaning is general: to be right or to guess correctly.

So Una corazonada permite acertar is a general statement.

If you want to be more specific, you could add an object or complement:

• Una corazonada permite acertar la respuesta.
• Una corazonada permite acertar con la decisión.

Spanish often leaves that unstated when speaking generally.

So Una corazonada permite acertar means something like:

• A hunch helps you get it right
• A hunch can lead one to the right answer

If you want to make the person explicit, you can add it:

• Una corazonada te permite acertar. = A hunch allows you to get it right.
• Una corazonada nos permite acertar. = A hunch allows us to get it right.

Without te, nos, etc., the sentence sounds more general and impersonal.

Yes, it is grammatical and understandable. It sounds like a general statement or a proverb-like observation.

In everyday speech, people might also say things like:

• Una corazonada te puede hacer acertar.
• A veces una corazonada te hace acertar.
• Una corazonada puede ser acertada.

But the original sentence is perfectly valid Spanish.