وَوُجُوهٌ يَوْمَئِذٍ عَلَيْهَا غَبَرَةٌ
Sentence structure
وُجُوهٌ introduces another nominal clause. Within its predicate clause, عَلَيْهَا is the fronted predicate and غَبَرَةٌ the delayed subject.
Ayah summary
Other faces on that Day will be covered with dust.
وَوُجُوهٌۭ — And faces
Grammar: وَ is a conjunction; وُجُوهٌ is a nominative broken-plural noun functioning as the outer topic.
يَوْمَئِذٍ — that Day
Grammar: يَوْمَئِذٍ is a time adverb functioning as the linked complement.
عَلَيْهَا — upon them
Grammar: عَلَى is a preposition and attached هَا its genitive pronoun; the complete phrase عَلَيْهَا is the fronted predicate in the inner nominal clause.
غَبَرَةٌۭ — (will be) dust
Grammar: A feminine indefinite nominative noun functioning as the delayed subject in the inner clause عَلَيْهَا غَبَرَةٌ.