Learned soaring number in concert (8)
I believe the answer is:
together
'in concert' is the definition.
(synonyms)
'learned soaring number' is the wordplay.
'learned' becomes 'got' (get can mean to learn or understand something).
'soaring' says the letters should be written in reverse (in a down clue, letters 'soar' up).
'number' becomes 'ether' (I've seen this before).
'got' reversed gives 'tog'.
'tog'+'ether'='TOGETHER'
(Other definitions for together that I've seen before include "Jointly" , "Appearing as a couple" , "On the trot" , "as a group" , "without a break?" .)