Composer hadn't, in short, finished symphony at the centre (5)
I believe the answer is:
haydn
'composer' is the definition.
(I know that Haydn is a composer)
'hadn't in short finished symphony at the centre' is the wordplay.
'in short' means to remove the last letter.
'finished symphony' becomes 'y' (I can't justify this - if you can you should believe this answer much more).
'at the centre' means one lot of letters goes inside another.
'hadnt' with its last letter taken off is 'hadn'.
'hadn' placed around 'y' is 'HAYDN'.
Can you help me to learn more?
(Other definitions for haydn that I've seen before include "Composer of over 100 symphonies" , "Austrian composer, d.1809" , "Creation composer" , "Esterhazy composer" , "Austrian symphonist, d. 1809" .)