Savoury dish, uncommonly good, needing while (7)
I believe the answer is:
rarebit
'savoury dish' is the definition.
(I've seen this before)
'uncommonly good needing while' is the wordplay.
'uncommonly good' becomes 'rare'.
'needing' is a charade indicator (letters next to each other).
'while' becomes 'bit' (both can mean an amount of time).
'rare'+'bit'='RAREBIT'
(Other definitions for rarebit that I've seen before include "which the Welsh take down?" , "on Welsh table?" , "cheesy meal" , "Arbiter (anag) -- snack" , "Melted cheese with ale on toast" .)