Elevated American rock group into smart, dominant position (9)
I believe the answer is:
supremacy
'dominant position' is the definition.
The answer and definition can be both states of affairs as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'elevated american rock group into smart' is the wordplay.
'elevated' shows that the letters should be reversed in order (in a down clue, letters go up).
'american' becomes 'US' (United States).
'rock group' becomes 'REM' (REM are a US rock band).
'into' is an insertion indicator.
'smart' becomes 'pacy' (I can't justify this - if you can you should give a lot more credence to this answer).
'us' reversed gives 'su'.
'rem' inserted within 'pacy' is 'premacy'.
'su'+'premacy'='SUPREMACY'
Can you help me to learn more?
(Other definitions for supremacy that I've seen before include "Highest power" , "Position of being in the highest authority" .)