Most of French paper's yellow (5)
I believe the answer is:
lemon
'yellow' is the definition.
(lemon is a kind of yellow)
I don't understand how the remainder of the clue works.
(Other definitions for lemon that I've seen before include "stinker" , "Pulsate" , "Yellow citrus fruit with acid taste" , "Tone" , "Shade of yellow - fruit" .)