They're the last to go to the wall (6,6)

I believe the answer is:

coping stones

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

'they're the last' is the definition.
The definition suggests an adverb but the answer is not.

'to go to the wall' is the wordplay.
I cannot quite understand how this works, but
'to' is present in the answer.
'go' could be 'ping' (pinging is a kind of going) and 'ping' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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.