Body established by Princess Anne having alternative informal title? (7)
I believe the answer is:
chassis
'body' is the definition.
(chassis is a kind of body)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for chassis that I've seen before include "Car's body" , "Vehicle's base frame" , "an estate may be built on it" , "sash" , "Car frame" .)