Not a lot can be seen in its yellowish light (3,4)

I believe the answer is:

fog lamp

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'light' is the definition.
(I know that Fog lamp is a type of light)

I don't understand the remainder of the clue.

(Other definitions for fog lamp that I've seen before include "It improves visibility" , "Something that's light" , "Bright light used in poor driving conditions" , "Strong car headlight" , "Driver's visibility aid in mist" .)

I've seen this clue in the Evening Standard.

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