Those doing it are out for the count (6)
I believe the answer is:
census
'the count' is the definition.
(census is a kind of count)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for census that I've seen before include "Official survey" , "People count" , "Periodic counting of the population" , "Official body count?" , "Periodic count by statisticians" .)