Complex in California, dull outside (9)
I believe the answer is:
intricate
'complex' is the definition.
(similar in meaning)
'in california dull outside' is the wordplay.
'california' becomes 'CA' (abbreviation).
'dull' becomes 'trite' (I've seen this before).
'outside' means one lot of letters goes inside another.
'ca' going within 'trite' is 'tricate'.
'in'+'tricate'='INTRICATE'
(Other definitions for intricate that I've seen before include "Convoluted" , "Very complicated and involved" , "Complex, labyrinthine" , "ornate" , "puzzlingly obscure" .)