Remove a blockage (6)
I believe the answer is:
unplug
'remove a blockage' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for unplug that I've seen before include "Disconnect (kettle or toaster?)" , "Remove power from" , "Disconnect (an electrical device)" , "Take out of socket" , "Remove from a socket" .)