إِنَّهُمْ يَكِيدُونَ كَيْدًۭا
Sentence structure
Attached هُمْ is the noun of إِنَّ. يَكِيدُونَ is its verbal predicate: attached و is the subject and final ن marks the indicative. كَيْدًۭا is a cognate accusative.
Ayah summary
The deniers continue to scheme against the truth.
إِنَّهُمْ — Indeed, they
Grammar: إِنَّ is an accusative/emphatic particle and attached هُمْ its third-person masculine-plural noun.
يَكِيدُونَ — are plotting
Grammar: A third-person masculine-plural indicative imperfect forming the predicate of إِنَّ. Attached و is the subject and final ن marks the indicative.
كَيْدًۭا — a plot
Grammar: An indefinite accusative verbal noun functioning as the cognate accusative of يَكِيدُونَ.