Это был не прямой ответ, а только ясный намёк, и я сразу всё поняла.

In the pattern Это был / Это была / Это было + noun, the past-tense form usually agrees with the noun that identifies это, not with это itself.

So here:

• ответ = masculine
• намёк = masculine

That is why Russian uses был.

Compare:

• Это была ошибка. = It was a mistake.
• Это было письмо. = It was a letter.

Because there is an explicit contrast: не ..., а ... = not ..., but ...

Russian normally writes не separately with adjectives when the sentence sets up this kind of opposition:

• не прямой ответ, а только ясный намёк
• не большой, а маленький
• не интересный, а скучный

If there were no such contrast, непрямой as one word could exist in other contexts and mean something like indirect.

Because а is the normal conjunction in the pattern не X, а Y = not X, but Y.

Here the speaker is correcting or replacing one description with another:

• not a direct answer
• but only a clear hint

Но also means but, but it is used differently. It usually introduces a stronger opposition to expectation, not this neat corrective pattern. In this sentence, а is the natural choice.

They are not direct objects here. They are predicate nouns after это был...:

• Это был ответ.
• Это был намёк.

So they stay in the nominative.

This is very common after это when you are identifying something. Compare:

• Это был мой брат.
• Это была шутка.

A learner may know that Russian often uses the instrumental after быть in the past, for example Он был учителем. That is true in many other sentence types, but with это был/была/было..., nominative is the normal choice.

Только means only or just.

So:

• а только ясный намёк = but only a clear hint

It emphasizes limitation: it was not a full, direct answer; it was merely a hint.

Here только modifies the whole noun phrase ясный намёк, not just the adjective.

Yes, ясный намёк is completely normal Russian.

A намёк is still indirect, but it can be very easy to understand. So ясный намёк means a hint that is obvious, unmistakable, or easy to catch.

English does the same thing:

• a clear hint
• a pretty obvious hint

So there is no contradiction for a native speaker.

In the past tense, Russian verbs agree with the subject in gender when the subject is singular.

With я:

• я понял = I understood (male speaker)
• я поняла = I understood (female speaker)

So я сразу всё поняла tells you that the speaker is female.

Because the sentence describes a completed moment of understanding.

• поняла = understood / got it
• понимала = was understanding / used to understand / understood in an ongoing sense

Here сразу shows that the understanding happened at once, as a single completed event. That fits the perfective verb понять.

So я сразу всё поняла means I immediately understood everything / I got it right away.

Because всё means everything or all of it, while все means everyone or all in the plural.

Here the speaker means I understood it all, so Russian uses всё.

Compare:

• Я всё поняла. = I understood everything.
• Я всех поняла. = I understood everyone.
• Все поняли. = Everyone understood.

Сразу means immediately, right away, or at once.

In я сразу всё поняла, it means the speaker understood the hint instantly.

Its position is fairly flexible:

• Я сразу всё поняла.
• Я всё сразу поняла.

Both are possible. The difference is mostly one of emphasis and rhythm, not basic meaning. The version in your sentence is very natural.

Russian punctuation requires them here.

1. Before а:
   A comma is standard before а when it connects contrasting parts:

   • не прямой ответ, а только ясный намёк

2. Before и:
   There is also a comma before и because it introduces another clause with its own subject and verb:

   • я
     • поняла

So the sentence has two coordinated clauses:

• Это был не прямой ответ, а только ясный намёк
• и я сразу всё поняла

It is pronounced na-MYOK.

The letter ё is important because it shows both the sound and the stress. In Russian, ё is always stressed.

So:

• намёк = hint
• stress on the second syllable

In some printed Russian, ё is often replaced by е, but learners should remember that the correct pronunciation here is still намёк, not намек with a plain e sound.