Tell us about the census (7)
I believe the answer is:
recount
'tell us' is the definition.
'recount' can be an answer for 'tell' (synonyms). I am unsure of the 'us' bit.
'about the census' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'the census' becomes 'count' (a census is a count of people).
're'+'count'='RECOUNT'
Can you help me to learn more?
(Other definitions for recount that I've seen before include "Give report" , "Tell in detail" , "post-election procedure?" , "Communicate" , "Go over details" .)