Meal in which diners help themselves to batter (6)
I believe the answer is:
buffet
I believe this is a double definition.
'meal in which diners help themselves' is the first definition.
(diners serve themselves at a buffet)
'batter' is the second definition.
(I know that batter can be written as buffet)
'to' is the link.
(Other definitions for buffet that I've seen before include "Wallop" , "place selling snacks" , "Refreshment counter - slap" , "self-service place" , "A self-help dining experience" .)