This should check population growth (6)
I believe the answer is:
census
This could be a double definition.
'this should' is the first definition.
The definition suggests a singular noun which matches the answer.
'check population growth' is the second definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
Can you help me to learn more?
(Other definitions for census that I've seen before include "Periodical population count" , "Head-count" , "Population survey" , "Official count of population" , "Periodic count as of population" .)