Graphic illustration of a city in a poor light (7)
I believe the answer is:
diagram
'graphic illustration' is the definition.
'diagram' can be an answer for 'illustration' (I've seen this before). I am unsure of the 'graphic' bit.
'city in a poor light' is the wordplay.
'city' becomes 'agra' (Indian city).
'in' is an insertion indicator.
'a poor light' becomes 'dim' (I am not sure about this - if you are sure you should believe this answer much more).
'agra' inserted inside 'dim' is 'DIAGRAM'.
'of a' is the link.
Can you help me to learn more?
(Other definitions for diagram that I've seen before include "Schematic drawing" , "Sketch - plan" , "Chart" , "Explanatory illustration" , "Explatory drawing" .)