Marc too upset by French procession (9)
I believe the answer is:
motorcade
'procession' is the definition.
(I know that motorcade is a type of procession)
'marc too upset by french' is the wordplay.
'upset by' indicates an anagram.
'french' becomes 'de' (I can't explain this - if you can you should believe this answer much more).
'marc'+'too'='marctoo'
'marctoo' anagrammed gives 'motorca'.
'motorca'+'de'='MOTORCADE'
Can you help me to learn more?
(Other definitions for motorcade that I've seen before include "Moving display" , "Car to demo (anag)" , "Procession using cars" , "Convoy" , "Procession of people in cars" .)