Criticises, but not re population survey (6)
I believe the answer is:
census
'population survey' is the definition.
(I've seen this before)
'criticises but not re' is the wordplay.
'criticises' becomes 'censures' (censuring is a kind of criticising).
'but not' is a deletion indicator.
'censures' with 're' taken out is 'CENSUS'.
(Other definitions for census that I've seen before include "Official body count?" , "Official count of population" , "Periodic count as of population" , "Population survey" , "Periodic counting of the population" .)