Salesman's pitch about large dish (7)
I believe the answer is:
platter
'large dish' is the definition.
(I've seen this in another clue)
'salesman's pitch about' is the wordplay.
'salesman's' becomes 'l' (I can't explain this - if you can you should believe this answer much more).
'pitch' becomes 'patter' (both can mean sales talk).
'about' indicates putting letters inside.
'l' put inside 'patter' is 'PLATTER'.
Can you help me to learn more?
(Other definitions for platter that I've seen before include "old record?" , "main course" , "Large flat serving dish" , "Charger" , "Salver" .)