Advice about border wind up southern range (3,7)
I believe the answer is:
the mendips
'range' is the definition.
(Mendip Hills)
'advice about border wind up southern' is the wordplay.
'advice' becomes 'tip' (I've seen this before).
'about' means one lot of letters goes inside another.
'border' becomes 'hem' (I've seen this before).
'wind up' becomes 'end' (I've seen this in other clues).
'southern' becomes 's' (abbreviation).
'hem'+'end'='hemend'
'tip' placed around 'hemend' is 'themendip'.
'themendip'+'s'='THE MENDIPS'
(Another definition for the mendips that I've seen is " heights".)