Hill is start of Appalachian trail (6)
I believe the answer is:
ascent
'hill' is the definition.
(I've seen this before)
'start of appalachian trail' is the wordplay.
'start of' says to take the initial letters.
'trail' becomes 'scent' (an animal's trail is its scent).
The initial letter of 'appalachian' is 'a'.
'a'+'scent'='ASCENT'
'is' acts as a link.
(Other definitions for ascent that I've seen before include "Going up" , "way up the mountain" , "An up-slope" , "A climb or way up" , "Enacts in climb" .)