Superior late meal, not small (5)
I believe the answer is:
upper
'superior' is the definition.
(eg an upper house in a parliament)
'late meal not small' is the wordplay.
'late meal' becomes 'supper' (I've seen this in another clue).
'not' is a deletion indicator.
'small' becomes 's' (abbreviation - e.g. clothes size).
'supper' with 's' taken out is 'UPPER'.
(Other definitions for upper that I've seen before include "Higher-ranking" , "form of stimulant" , "Higher in place or position" , "The higher of two, berths perhaps" , "Higher; part of shoe" .)