Deadlock, blockage (6)
I believe the answer is:
logjam
I believe this is a double definition.
'deadlock' is the first definition.
(I've seen this before)
'blockage' is the second definition.
(I've seen this before)
(Other definitions for logjam that I've seen before include "deadlock" , "Major stoppage" , "blockage" , "impasse" , "bottleneck" .)