Assuming success brought about out-and-out gains (8)
I believe the answer is:
arrogant
'assuming success brought about out-and-out gains' is the definition.
I can't tell whether this definition defines the answer.
'assuming success brought about out-and-out' is the wordplay.
'assuming' indicates putting letters inside.
'success' becomes 'go' (I've seen this in other clues).
'brought about' shows that the letters should be reversed in order.
'out-and-out' becomes 'arrant' ('arrant' can be a synonym of 'out-and-out').
'go' in reverse letter order is 'og'.
'og' placed into 'arrant' is 'ARROGANT'.
Can you help me to learn more?
(Other definitions for arrogant that I've seen before include "Proud and contemptuous" , "Overly self-important" , "Conceited, self-important" , "Having an exaggerated sense of one's own importance" , "Overbearing with exaggerated sense of superiority" .)