Green team working in harmony (9)
I believe the answer is:
agreement
'harmony' is the definition.
(agreement is a kind of harmony)
'green team working' is the wordplay.
'working' is an anagram indicator.
'green'+'team'='greenteam'
'greenteam' with letters rearranged gives 'AGREEMENT'.
'in' acts as a link.
(Other definitions for agreement that I've seen before include "Correspondence" , "legal contract maybe" , "concert" , "Conformity" , "Harmony, concurrence" .)