Field division that takes years to train (8)
I believe the answer is:
hedgerow
This could be a double definition.
'field division that takes years' is the first definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
'train' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'to' is the link.
Can you help me to learn more?
(Other definitions for hedgerow that I've seen before include "natural fence" , "Line of shrubs as barrier" , "Bushy boundary" , "Living boundary between fields" , "Line of entwined bushes and trees" .)