Charged a lot in Californian city retreat (5)
I believe the answer is:
laden
'charged a lot' is the definition.
(loaded or charged with a lot)
'californian city retreat' is the wordplay.
'californian city' becomes 'la'.
'retreat' becomes 'den' (both can mean a lair or hideout).
'la'+'den'='LADEN'
'in' is the link.
(Other definitions for laden that I've seen before include "'Burdened, oppressed (5)'" , "charged a lot" , "Freighted" , "Like cargo boat" , "full cargo ship" .)