Superior total, sealing game up (8)
I believe the answer is:
arrogant
'superior' is the definition.
(I've seen this before)
'total sealing game up' is the wordplay.
'total' becomes 'arrant' (old-fashioned term meaning complete or utter).
'sealing' means one lot of letters goes inside another (inserted letters are sealed inside).
'game' becomes 'go' (go game is a kind of game).
'up' is a reversal indicator (in down clue: letters go upwards).
'go' back-to-front is 'og'.
'arrant' placed around 'og' is 'ARROGANT'.
(Other definitions for arrogant that I've seen before include "Showing an offensive sense of superiority" , "Disdainful" , "Overbearing; conceited" , "Overly self-important" , "Conceited, self-important" .)