One eating a piece of celery with too much noise (5)
I believe the answer is:
diner
'one eating' is the definition.
(I've seen this before)
'a piece of celery with too much noise' is the wordplay.
'a piece of celery' becomes 'er' (I am not sure about this - if you are sure you should believe this answer much more).
'with' is a charade indicator (letters next to each other).
'too much noise' becomes 'din' (I've seen this before).
'er' put after 'din' is 'DINER'.
Can you help me to learn more?
(Other definitions for diner that I've seen before include "American restaurant" , "Restaurant client" , "Restaurant customer" , "Eater" , "One eating a meal" .)