Border where dog barking (8)
I believe the answer is:
hedgerow
'border' is the definition.
(I've seen this before)
'where dog barking' is the wordplay.
'barking' indicates anagramming the letters (UK slang for mad).
'where'+'dog'='wheredog'
'wheredog' is an anagram of 'HEDGEROW'.
(Other definitions for hedgerow that I've seen before include "Field boundary" , "Living boundary between fields" , "Line of entwined bushes and trees" , "Growth around field" , "natural fence" .)