Collusion? California loudly shows disapproval (7)
I believe the answer is:
cahoots
'collusion?' is the definition.
(to be 'in cahoots' is to collude with someone)
'california loudly shows disapproval' is the wordplay.
'california' becomes 'ca'.
'loudly shows disapproval' becomes 'hoots' (to hoot is to make a loud noise when cheering).
'ca'+'hoots'='CAHOOTS'
(Other definitions for cahoots that I've seen before include "(In) conspiracy" , "In - means colluding" , "In such agreement" , "League" , "Collusion" .)