Smog left brown colour (5)

I believe the answer is:

hazel

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'brown colour' is the definition.
'hazel' can be an answer for 'brown' (thesaurus). I'm unsure of the 'colour' bit.

'smog left' is the wordplay.
'smog' becomes 'haze' (I can't justify this - if you can you should believe this answer much more).
'left' becomes 'l' (common abbreviation).
'haze'+'l'='HAZEL'

Can you help me to learn more?

(Other definitions for hazel that I've seen before include "Tree with catkins" , "Catkin shrub" , "Yellow-brown - nut-tree" , "wood" , "Light brown; nut" .)

I've seen this clue in The Times.

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