Taj Mahal's location included in obscure plan (7)
I believe the answer is:
diagram
'plan' is the definition.
(I've seen this in another clue)
'taj mahal's location included in obscure' is the wordplay.
'taj mahal's location' becomes 'agra' (I've seen this in another clue).
'included in' indicates putting letters inside.
'obscure' becomes 'dim' (both can mean dark).
'agra' put inside 'dim' is 'DIAGRAM'.
(Other definitions for diagram that I've seen before include "scheme" , "Chart" , "I'm a drag (anag)" , "Schematic representation" , "Drawing to show how things work" .)