Mortality figures may be a complete write-off (4,4)
I believe the answer is:
dead loss
'write-off' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for dead loss that I've seen before include "unprofitable" , "Dud" , "Totally useless item" , "Unproductive person or thing" , "write-off" .)