Mist (3)
(Other definitions for fog that I've seen before include "Thick mist" , "Bafflement" , "Heavy mist" , "Miasma" , "Obscure" .)
'mist' is the definition.
(haze can mean a mist)
This is the entire clue.
(Other definitions for haze that I've seen before include "Mist or shimmer due to heat" , "State of mental confusion - mist" , "Lack of definition or precision" , "Vapour" , "Daze, fog" .)