Will it prevent death or deal a fatal blow? (4,9)
I believe the answer is:
life preserver
'a fatal blow?' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'will it prevent death or deal' is the wordplay.
I cannot quite understand how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found within the answer.
'deal' could be 'serve' (I've seen this before) and 'serve' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for life preserver that I've seen before include "Cosh; (US) inflatable jacket" , "club" , "The Mae West" , "Bludgeon used for self-defence" , "Cosh (paradoxically)" .)