Musical has inevitable content (5)
I believe the answer is:
evita
'musical' is the definition.
(Andrew Lloyd Webber musical)
'has inevitable content' is the wordplay.
'content' says the answer is hidden in the clue (letters contained within the clue).
'EVITA' is hidden within 'has inevitable'.
(Other definitions for evita that I've seen before include "Famous musical" , "1996 musical film, starring Madonna" , "Well-known musical" , "Juan Peron's wife" , "Musical based on Argentine leader" .)