Exaggerated concerning key identification (7)
I believe the answer is:
overdid
'exaggerated' is the definition.
('overdo' can be a synonym of 'exaggerate')
'concerning key identification' is the wordplay.
'concerning' becomes 'over' (both can mean relating to).
'key' becomes 'd' (musical key).
'identification' becomes 'ID' (abbreviation).
'over'+'d'+'id'='OVERDID'
(Other definitions for overdid that I've seen before include "went too far" , "Exaggerated" , "Made too much of" , "operated excessively" .)