Retrieve cards, doubling black suits (6)
I believe the answer is:
access
'retrieve' is the definition.
(accessing is a kind of retrieving)
I cannot understand how the rest of the clue works.
(Other definitions for access that I've seen before include "outburst" , "Means of admittance or entrance" , "Admission" , "Way in, means of approach" , "Approach/enter (a place)" .)