Moody policeman (4)
I believe the answer is:
blue
This clue could be a double definition.
'moody' is the first definition.
(thesaurus)
'policeman' is the second definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
Can you help me to learn more?
(Other definitions for blue that I've seen before include "Dejected" , "Down in the mouth" , "Dirty" , "Such humour < makes conservative" , "Spend all at once - colour" .)