Officer rose, say, accepting one good promotion (9)
I believe the answer is:
brigadier
'officer' is the definition.
(I know that brigadier is a type of officer)
'rose say accepting one good promotion' is the wordplay.
'rose say' becomes 'brier' (I can't explain this - if you can you should give a lot more credence to this answer).
'accepting' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'good' becomes 'g' (abbreviation).
'promotion' becomes 'ad' (short for advert).
'i'+'g'+'ad'='igad'
'brier' going around 'igad' is 'BRIGADIER'.
Can you help me to learn more?
(Other definitions for brigadier that I've seen before include "Air bridge over to the military officer" , "Officer in charge of army unit, part of division" , "Military leader" , "Rank above colonel" , "High-ranking army officer" .)