Unstable California city's anger (6)
I believe the answer is:
labile
'unstable' is the definition.
('labile' can be similar in meaning to 'unstable')
'california city's anger' is the wordplay.
'california city' becomes 'la' (Los Angeles).
'anger' becomes 'bile'.
'la'+'bile'='LABILE'
(Other definitions for labile that I've seen before include "Open to change, adaptable - i.e. ball" , "easily changed" , "(Chemically) unstable" .)