Fairground ride to be exciting in California (8)
I believe the answer is:
carousel
'fairground ride' is the definition.
(carousels are often found at fairgrounds)
'to be exciting in california' is the wordplay.
'to be exciting' becomes 'rouse' (rouse can mean to excite).
'in' means one lot of letters goes inside another.
'california' becomes 'cal' (short for California).
'rouse' placed within 'cal' is 'CAROUSEL'.
(Other definitions for carousel that I've seen before include "Rodgers/Hammerstein hit" , "Luggage conveyor belt and fairground ride" , "fair entertainment?" , "Rotating conveyor" , "Musical - merry-go-round" .)