Substitute opening scene with casting lady? (6)
I believe the answer is:
switch
'substitute' is the definition.
(I've seen this before)
'opening scene with casting lady?' is the wordplay.
'opening' says to take the initial letters.
'with' means one lot of letters go next to another.
'casting lady?' becomes 'witch' (I've seen this in another clue).
The first letter of 'scene' is 's'.
's'+'witch'='SWITCH'
(Other definitions for switch that I've seen before include "Exchange; contactor" , "Control for making or breaking connections" , "Change - debit card" , "Change or exchange" , "Change round" .)