Musical Director turned up in case (6)
I believe the answer is:
dative
'case' is the definition.
(dative is a kind of case)
'musical director turned up' is the wordplay.
'musical' becomes 'evita' (I've seen this before).
'director' becomes 'd'.
'turned up' says the letters should be written in reverse.
'evita'+'d'='evitad'
'evitad' backwards is 'DATIVE'.
'in' acts as a link.
(Other definitions for dative that I've seen before include "Grammatical case" , "'To' case (grammar)" .)