Co-operation (8)
I believe the answer is:
teamwork
'co-operation' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for teamwork that I've seen before include "It demands action by several folk" , "Co-ordination" , "Organised co-operation, group endeavour." , "Combined action of a group" , "Effective action of a group" .)