وَمَآ أَدْرَىٰكَ مَا ٱلْعَقَبَةُ
Sentence structure
مَآ is interrogative. أَدْرَىٰكَ is a Form IV perfect with understood subject هُوَ and attached كَ as first object; مَا ٱلْعَقَبَةُ is its second object, a nominal question with ٱلْعَقَبَةُ as predicate.
Ayah summary
And what will make you understand what that difficult ascent is?
وَمَآ — And what
Grammar: وَ coordinates/resumes and مَآ is an interrogative pronoun functioning as the topic.
أَدْرَىٰكَ — can make you know
Grammar: A Form IV third-person masculine-singular perfect with understood subject هُوَ; attached كَ is its first object.
مَا — what
Grammar: An interrogative pronoun functioning as the topic of the nominal question and together with its predicate as the second object of أَدْرَىٰكَ.
ٱلْعَقَبَةُ — the steep path (is)
Grammar: ٱل defines the feminine-singular nominative predicate of interrogative مَا.