Passage which Cockney has to be finished? (4)
I believe the answer is:
adit
'passage' is the definition.
(passage leading to a mine)
I don't understand how the remainder of the clue works.
(Other definitions for adit that I've seen before include "Passageway into a mine" , "Mine opening" , "Da, it is a mine entrance" , "Horiz. mine entrance" , "Mine-shaft" .)