Witter on about replacing a British dish (7)
I believe the answer is:
rarebit
'dish' is the definition.
(rarebit is a kind of dish)
'witter on about replacing a british' is the wordplay.
I cannot quite understand how this works, but
'on' could be 're' ('on' can be mean 'with reference to') and 're' is located in the answer.
'about' could be 'a' (abbreviation in Chambers) and 'a' is located in the answer.
'british' could be 'b' (abbreviation e.g. in 'BBC') and 'b' is found within the answer.
The remaining letters 'rit' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for rarebit that I've seen before include "Welsh snack" , "mouthful?" , "Dish of grilled cheese on toast" , "Arbiter of traditional Welsh dish" , "See 8 Across" .)