Don't shoot him for telling you jam's weirdly green (9)
I believe the answer is:
messenger
'don't shoot him for telling' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'jam's weirdly green' is the wordplay.
'jam's' becomes 'mess'' ('mess' can be a synonym of 'jam').
'weirdly' indicates an anagram.
'green' anagrammed gives 'enger'.
'mess'+'enger'='MESSENGER'
'you' is the link.
Can you help me to learn more?
(Other definitions for messenger that I've seen before include "Person carrying information to another" , "Runner" , "He takes note" , "Communication carrier" , "He's just bringing the word - don't shoot him" .)