Small but superior meal (6)
I believe the answer is:
supper
'meal' is the definition.
(supper is a kind of meal)
'small but superior' is the wordplay.
I cannot quite see how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is found in the answer.
'superior' could be 'upper' (eg an upper house in a parliament) and 'upper' is located in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for supper that I've seen before include "consumer" , "Light evening meal" , "singing for this?" , "Evening repast" , "Evening 2 Down" .)