Greek character circles ship, beginning to survey frame (7)
I believe the answer is:
chassis
'frame' is the definition.
(base frame of a vehicle)
'greek character circles ship beginning to survey' is the wordplay.
'greek character' becomes 'chi' (letter from the Greek alphabet).
'circles' is an insertion indicator.
'ship' becomes 'ass' (I can't explain this - if you can you should give a lot more credence to this answer).
'beginning to' suggests taking the first letters.
The initial letter of 'survey' is 's'.
'chi' going around 'ass' is 'chassi'.
'chassi'+'s'='CHASSIS'
Can you help me to learn more?
(Other definitions for chassis that I've seen before include "Car's body" , "Main frame (of vehicle etc)" , "basic structure" , "an estate may be built on it" , "Body frame" .)