Popular musical regularly billed "Unavoidable" (10)
I believe the answer is:
inevitable
'unavoidable' is the definition.
(similar in meaning)
'popular musical regularly billed' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'musical' becomes 'evita' (Andrew Lloyd Webber musical).
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'billed' are 'ble'.
'in'+'evita'+'ble'='INEVITABLE'
(Other definitions for inevitable that I've seen before include "Inescapable" , "Unavoidable, fated" , "Certain to happen" .)