Failure of French newspaper, reactionary editor dismissed (5)
I believe the answer is:
lemon
'failure' is the definition.
(lemon can mean a failure or useless person)
I can't explain the rest of the clue.
(Other definitions for lemon that I've seen before include "Useless object" , "failure" , "Yellow fruit (it's also the answer!)" , "Feeble thing (colloq.); fruit tree" , "Acidic fruit" .)