City after six can be quite stimulating (4)
I believe the answer is:
agra
'city' is the definition.
(Indian city)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for agra that I've seen before include "Indian masterpiece" , "Subcontinental city" , "Indian city, capital of the Mogul empire until 1658" , "mausoleum site" , "tourist centre" .)