Dish erstwhile bar concocted (5,7)
I believe the answer is:
welsh rarebit
'dish' is the definition.
(Welsh rarebit is an example)
'erstwhile bar concocted' is the wordplay.
'concocted' indicates anagramming the letters.
'erstwhile'+'bar'='erstwhilebar'
'erstwhilebar' anagrammed gives 'WELSH RAREBIT'.
(Other definitions for welsh rarebit that I've seen before include "Cheese on toast" , "cheesy meal" , "Toasted snack" , "Cheesy dish" .)