Disappointment of French omitted from their paper (5)
I believe the answer is:
lemon
'paper' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for lemon that I've seen before include "Strong yellow colour" , "A fruit; a worthless item" , "Leaving body" , "Sharp-tasting fruit" , "Pulsate" .)