Indian city is involved in obscure scheme (7)
I believe the answer is:
diagram
'scheme' is the definition.
(I know that scheme can be written as diagram)
'indian city is involved in obscure' is the wordplay.
'indian city' becomes 'agra' (I've seen this in another clue).
'is involved in' indicates putting letters inside.
'obscure' becomes 'dim' (both can mean dark).
'agra' put into 'dim' is 'DIAGRAM'.
(Other definitions for diagram that I've seen before include "Explatory drawing" , "Chart" , "Sketch - plan" , "scheme" , "A grid, Ma? (Anag)" .)