Affair; collaboration (7)
I believe the answer is:
liaison
I believe this is a double definition.
'affair' is the first definition.
(I know that affair can be written as liaison)
'collaboration' is the second definition.
(I've seen this before)
(Other definitions for liaison that I've seen before include "Sort of officer" , "Amour; communication" , "Mediator" , "Naughty affair?" , "A contact or affair" .)