When to tell all? (6)
I believe the answer is:
census
'tell all?' is the definition.
'census' can be an answer for 'tell' (thesaurus). I am unsure of the 'all?' bit.
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 "Periodic count as of population" , "Official survey" , "Official body count?" , "Periodical population count" , "Head count" .)