Association, connection (7)
I believe the answer is:
linkage
I believe this is a double definition.
'association' is the first definition.
(I've seen this in another clue)
'connection' is the second definition.
(I know that linkage is a type of connection)
(Other definitions for linkage that I've seen before include "System of connections" , "where the join is" , "Connection, bond" , "Connection, coupling" , "Part of mechanism" .)