كَلَّآ إِنَّهَا تَذْكِرَةٌ
Sentence structure
كَلَّآ is a deterrent particle. In the emphatic nominal clause, the attached pronoun is the subject of إِنَّ and تَذْكِرَةٌ its predicate.
Ayah summary
The Quran is a universal reminder and does not depend on the acceptance of the arrogant.
كَلَّآ — Nay
Grammar: كَلَّآ is a deterrent particle.
إِنَّهَا — Indeed, it
Grammar: إِنَّ is an accusative and emphatic particle. Attached هَا is its noun.
تَذْكِرَةٌۭ — (is) a reminder
Grammar: nominative noun functioning as the predicate of inna.