Those marked to be rubbed out? (3,4)
I believe the answer is:
hit list
'out?' is the definition.
Both the answer and definition are singular nouns.
Maybe you can see an association between them that I don't see?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for hit list that I've seen before include "Those chosen for attack" , "Successes in the music industry" , "Names to be rubbed out?" , "Names of victims to be" , "Assassin's potential workload?" .)