Dig up doctor at the border (6)
I believe the answer is:
dredge
'dig up' is the definition.
(I've seen this in another clue)
'doctor at the border' is the wordplay.
'doctor' becomes 'dr' (abbreviation).
'at' is a charade indicator (letters next to each other).
'the border' becomes 'edge' (synonyms).
'dr'+'edge'='DREDGE'
(Other definitions for dredge that I've seen before include "Drag up" , "Scoop mud from, say, harbour" , "Sort of collector" , "Dig out mud from (waterway)" , "Clean out the bed of a river or harbour" .)