Some ground article goes on about twice (4)
I believe the answer is:
acre
'some ground' is the definition.
(acre is a measure of land)
'article goes on about twice' is the wordplay.
I cannot really understand how this works, but
'article' could be 'a' (the indefinite article in English) and 'a' is found in the answer.
'on' could be 're' ('on' can be mean 'with reference to') and 're' is found in the answer.
'about' could be 'c' (abbreviation for circa) and 'c' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for acre that I've seen before include "A state of W Brazil" , "in Western Brazil" , "Crusaders battlefield, now in Israel" , "Muslims here besieged" , "Square measure of land" .)