Exaggerated discussion initially supporting old composer (7)
I believe the answer is:
overdid
'exaggerated' is the definition.
('overdo' can be a synonym of 'exaggerate')
'discussion initially supporting old composer' is the wordplay.
'initially' indicates taking the first letters.
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'old' becomes 'o' (abbreviation).
'composer' becomes 'verdi' (Giuseppe Verdi 1813-1901).
The first letter of 'discussion' is 'd'.
'o'+'verdi'='overdi'
'd' after 'overdi' is 'OVERDID'.
(Other definitions for overdid that I've seen before include "operated excessively" , "went too far" , "Exaggerated" , "Made too much of" .)