He brings news of chaos at the Green Rally (9)
I believe the answer is:
messenger
'he brings news' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'chaos at the green rally' is the wordplay.
I cannot really see how this works, but
'chaos' could be 'mess' (I've seen this in another clue) and 'mess' is present in the answer.
an anagram of 'green' is 'enger' which is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for messenger that I've seen before include "Courier - don't shoot him" , "Bearer of communication" , "Delivery boy" , "He takes note" , "One doing errands" .)