Fog drifting in from Istanbul? (4)

I believe the answer is:

mist

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

'fog drifting' is the definition.
'mist' can be an answer for 'fog' ('mist' can be a synonym of 'fog'). I'm not certain of the 'drifting' bit.

'in from istanbul?' is the wordplay.
'in' indicates the answer is hidden within the clue.
'MIST' is hidden within 'from istanbul'.

Can you help me to learn more?

(Other definitions for mist that I've seen before include "Obscure" , "Mizzle; light rain" , "Thin layer of fog" , "Slight fog" , "Haze" .)

I've seen this clue in the Evening Standard.

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