Block of stone in coalpit oddly disappearing in a few weeks (8)

I believe the answer is:

monolith

I'm a little stuck... Click here to teach me more about this clue!

(Other definitions for monolith that I've seen before include "Statue from one block of stone" , "Big pillar" , "Large corporation" , "Monument of a large standing stone" , "Pillar-like stone" .)

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app