إِنَّ عَلَيْنَا لَلْهُدَىٰ
Sentence structure
إِنَّ begins an emphatic nominal clause. عَلَيْنَا is a prepositional phrase in the predicate construction; لَلْهُدَىٰ contains emphatic lām and the accusative noun of إِنَّ.
Ayah summary
Surely it is for Us to make the straight way clear.
إِنَّ — Indeed
Grammar: An emphatic particle that makes its noun accusative and predicate nominative. The clause introduced by «إِنَّ» has an omitted predicate.
عَلَيْنَا — upon Us
Grammar: عَلَىٰ is a preposition and attached نَا a first-person-plural genitive pronoun; the phrase belongs to the predicate construction. This phrase is linked through an omitted element.
لَلْهُدَىٰ — is the guidance
Grammar: Emphatic لَ precedes ٱلْهُدَىٰ, the accusative noun of إِنَّ.