Combined musical performance ends oddly (9)
I believe the answer is:
concerted
'combined' is the definition.
('concerted' can be a synonym of 'combined')
'musical performance ends oddly' is the wordplay.
'musical performance' becomes 'concert' (I've seen this before).
'oddly' means one should take alternating letters.
The alternate letters of 'ends' are 'ed'.
'concert'+'ed'='CONCERTED'
(Other definitions for concerted that I've seen before include "Effortful" , "Combined" .)