Tomb site covering over marketplace once (5)
I believe the answer is:
agora
'tomb site' is the definition.
'agora' can be an answer for 'site' (thesaurus). I'm not certain of the 'tomb' bit.
'covering over marketplace once' is the wordplay.
'covering' means one lot of letters goes inside another.
'over' becomes 'o' (cricket abbreviation).
'marketplace once' becomes 'agra' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'o' going into 'agra' is 'AGORA'.
Can you help me to learn more?
(Other definitions for agora that I've seen before include "Ancient Greek assembly place" , "market in Athens" , "One hundredth of a shekel" , "Place to gather" , "Marketplace in ancient Greece" .)