Casualty cast sacrificing time for rehearsal at last (4)
I believe the answer is:
loss
'casualty' is the definition.
(loss is a kind of casualty)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for loss that I've seen before include "sacrifice?" , "Defeat (in sport)" , "Bandleader" , "(Sporting) defeat" , "Financial reverse" .)