Border of hedges (4)
I believe the answer is:
edge
'border' is the definition.
(synonyms)
'of hedges' is the wordplay.
'of' indicates the answer is hidden within the clue.
'EDGE' is hidden within 'hedges'.
(Other definitions for edge that I've seen before include "Margin, outside limit" , "Rim or slight advantage" , "Rim or sharp side of knife" , "Side, brink" , "Guitarist with U2" .)