فَأَنذَرْتُكُمْ نَارًا تَلَظَّىٰ
Sentence structure
فَأَنذَرْتُكُمْ is Form IV: attached تُ is subject and كُمْ first object. نَارًا is the second object; تَلَظَّىٰ is its adjectival clause.
Ayah summary
So We have warned you of a blazing fire.
فَأَنذَرْتُكُمْ — So I warned you
Grammar: فَ resumes; أَنذَرْ is Form IV, attached تُ subject and كُمْ first object.
نَارًۭا — of a Fire
Grammar: An indefinite feminine accusative second object of أَنذَرْتُكُمْ.
تَلَظَّىٰ — blazing
Grammar: A third-person feminine-singular imperfect with understood subject هِيَ; its clause describes نَارًا.