Shout about everything (4)
I believe the answer is:
call
'shout' is the definition.
(I know that shout can be written as call)
'about everything' is the wordplay.
'about' becomes 'c' (abbreviation for 'circa').
'everything' becomes 'all' (all things).
'c'+'all'='CALL'
(Other definitions for call that I've seen before include "Visit; shout" , "Assign a name to" , "That is enough" , "Be in control" , "Phone - demand" .)