Came back with European socialist support for census (9)
I believe the answer is:
countered
'came back' is the definition.
(counter can mean to come back or reply)
'european socialist support for census' is the wordplay.
'european' becomes 'E' (abbreviation e.g. EU).
'socialist' becomes 'red' (socialism is often associated with the colour red).
'support for' says to put letters next to each other.
'census' becomes 'count' (a census is a count of people).
'e'+'red'='ered'
'ered' after 'count' is 'COUNTERED'.
'with' acts as a link.
(Other definitions for countered that I've seen before include "Answered a chess move" , "Opposed" , "returned" , "Contradicted" .)