Advantage where bushy boundary has front clipped (4)
I believe the answer is:
edge
'advantage' is the definition.
(having the edge is having an advantage)
'bushy boundary has front clipped' is the wordplay.
'bushy boundary' becomes 'hedge' (boundary formed by shrubbery).
'has front clipped' means to remove the first letter (the letter at the front is clipped off).
'hedge' with its first letter taken off is 'EDGE'.
'where' is the link.
(Other definitions for edge that I've seen before include "Outer limit" , "Sidle, lip" , "marginal advantage" , "Final line" , "Force" .)