Damage practical lesson about earth, regarding many headstones? (9)

I believe the answer is:

marmoreal

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

'damage practical lesson about earth regarding many headstones?' is the definition.
I can't judge whether this defines the answer.

'damage practical lesson about earth' is the wordplay.
'damage' becomes 'mar' (to mar is to spoil or damage).
'practical lesson' becomes 'moral' (I've seen this before).
'about' indicates putting letters inside.
'earth' becomes 'E'.
'moral' placed around 'e' is 'moreal'.
'mar'+'moreal'='MARMOREAL'

Can you help me to learn more?

(Other definitions for marmoreal that I've seen before include "of fine stone" , "stony cold" , "made of stone" .)

I've seen this clue in The Independent.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.