One leaving departs ancient city ruin (7)
I believe the answer is:
destroy
'ruin' is the definition.
(I know that ruin can be written as destroy)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for destroy that I've seen before include "Soundly defeat" , "Wreck" , "Flatten" , "Get rid of" , "Demolish; pull down" .)