Headless maggot snaffled by young canary (9)
I believe the answer is:
informant
'headless maggot' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'snaffled by young canary' is the wordplay.
'snaffled by' is an insertion indicator (snaffle means to take or steal).
'young' becomes 'infant' (similar in meaning).
'canary' becomes 'orm' (I can't explain this - if you can you should believe this answer much more).
'infant' going around 'orm' is 'INFORMANT'.
Can you help me to learn more?
(Other definitions for informant that I've seen before include "One who sings" , "Rat" , "source of dope" , "Sneak" , "Telltale" .)