Diagram sometimes accompanied by a photo (5)

I believe the answer is:

graph

I'm a little stuck... Click here to teach me more about this clue!

'diagram' is the definition.
(I know that graph is a more specific form of diagram)

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for graph that I've seen before include "Plotted diagram" , "Diagram showing the relationship between variable quantities" , "Geometrical diagram" , "Drawing showing relationship between quantities" , "Diagram showing relationships between things" .)

I've seen this clue in the Evening Standard.

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