Communications muddle involving Green (8)
I believe the answer is:
messages
'communications' is the definition.
(message is a kind of communication)
'muddle involving green' is the wordplay.
'muddle' becomes 'mess' ('mess' can be a synonym of 'muddle').
'involving' means one lot of letters goes inside another.
'green' becomes 'sage' (sage green is a kind of green**).
'mess' enclosing 'sage' is 'MESSAGES'.
(Other definitions for messages that I've seen before include "Pieces of information carried from one person to another" , "Communications from one person to another" , "Communications, written, spoken or signalled" , "Brief communications" , "Communications or errands" .)