Musical and ballet, oddly, can be avoided (8)
I believe the answer is:
evitable
'can be avoided' is the definition.
(not inevitable)
'musical and ballet oddly' is the wordplay.
'musical' becomes 'evita' (Andrew Lloyd Webber musical).
'and' means one lot of letters go next to another.
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
The alternating letters of 'ballet' are 'ble'.
'evita'+'ble'='EVITABLE'
(Other definitions for evitable that I've seen before include "Live beat can be avoidable" , "could be avoided" .)