Diagram having no place, being very faint (3)

I believe the answer is:

dim

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'faint' is the definition.
(I know that faint can be written as dim)

I don't understand the rest of the clue.

(Other definitions for dim that I've seen before include "Somewhat out of sight" , "Badly lit or not so bright" , "Slow to learn" , "Without much light" , "Lacking in light" .)

I've seen this clue in the Evening Standard.

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