Over that one cannot take stock (6,4)
I believe the answer is:
cattle-grid
'over that one cannot take stock' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'over that one cannot take stock' is the wordplay.
'over' means one lot of letters go next to another (in a down clue, some letters go over others).
'that one cannot take' becomes 'grid' (I can't justify this - if you can you should believe this answer much more).
'stock' becomes 'cattle' (I've seen this before).
'grid' put after 'cattle' is 'CATTLE-GRID'.
Can you help me to learn more?
(Other definitions for cattle-grid that I've seen before include "Hollow in road with bars across" , "Barrier to animals but not to vehicles" .)